Nonpregnant Control Rats Research Articles

Rapid gastric emptying during pregnancy in a rat model

Background/aimsThe effect of pregnancy on gastric emptying has not been established, although the predominant clinical assumption is that gastric emptying is delayed during pregnancy. We hypothesized that the rate of emptying of nutrients during pregnancy is not delayed, but is actually more rapid when compared to the non-pregnant state. The rate of gastric emptying is a major determinant of postprandial glucose elevations. Materials and methods24 female and 4 male Spague-Dawley rats were used. Female rats were randomly divided into two groups: eight rats for the control group and sixteen rats for the pregnant group. Using physiologic, non-traumatic nuclear medicine scintigraphy imaging methodology, the authors studied gastric emptying of a liquid mixed meal in pregnant rats and non-pregnant controls. Body weights, daily food ingestion, and the rate of nutrient gastric emptying were recorded in both groups at pre-pregnancy, early pregnancy, and late pregnancy. ResultsThe authors found that pregnancy in this rat model is associated with a 37–43% increased rate of nutrient gastric emptying from the stomach in late pregnancy as compared to non-pregnant control rats and pre-pregnancy rats. ConclusionThese findings contradict the current clinical assumption that gastric emptying is delayed in pregnancy. If further studies confirm a more rapid gastric emptying rate during human pregnancy, new therapies aimed at slowing the rate of nutrient absorption should be considered for the prevention and treatment of pregnancy-associated nausea, gestational diabetes, and other insulin-resistant pregnancy-associated states such as pre-eclampsia.

A low‐protein diet during pregnancy alters glucose metabolism and insulin secretion

In pancreatic islets, glucose metabolism is a key process for insulin secretion, and pregnancy requires an increase in insulin secretion to compensate for the typical insulin resistance at the end of this period. Because a low-protein diet decreases insulin secretion, this type of diet could impair glucose homeostasis, leading to gestational diabetes. In pancreatic islets, we investigated GLUT2, glucokinase and hexokinase expression patterns as well as glucose uptake, utilization and oxidation rates. Adult control non-pregnant (CNP) and control pregnant (CP) rats were fed a normal protein diet (17%), whereas low-protein non-pregnant (LPNP) and low-protein pregnant (LPP) rats were fed a low-protein diet (6%) from days 1 to 15 of pregnancy. The insulin secretion in 2.8 mmol l(-1) of glucose was higher in islets from LPP rats than that in islets from CP, CNP and LPNP rats. Maximal insulin release was obtained at 8.3 and 16.7 mmol l(-1) of glucose in LPP and CP groups, respectively. The glucose dose-response curve from LPNP group was shifted to the right in relation to the CNP group. In the CP group, the concentration-response curve to glucose was shifted to the left compared with the CNP group. The LPP groups exhibited an "inverted U-shape" dose-response curve. The alterations in the GLUT2, glucokinase and hexokinase expression patterns neither impaired glucose metabolism nor correlated with glucose islet sensitivity, suggesting that β-cell sensitivity to glucose requires secondary events other than the observed metabolic/molecular events.

Toll-Like Receptor 3 Activation During Pregnancy Elicits Preeclampsia-Like Symptoms in Rats

Preeclampsia (PE), a pregnancy-specific hypertensive syndrome, is one of the leading causes of premature births as well as fetal and maternal death. There is strong evidence that maternal immune system activation, of which Toll-like receptors (TLRs) play a major role, contributes to the development of PE. Viral infections, sensed by TLR3, are associated with hypertensive disorders of pregnancy. We tested the hypothesis that TLR3 activation during pregnancy would cause hypertension, endothelial dysfunction, proteinuria, and intrauterine growth restriction in normal pregnant rats. We treated pregnant and nonpregnant rats with the viral mimetic polyinosinic:polycytidylic acid (poly I:C) or vehicle every other day beginning at day 10 of gestation and measured systolic blood pressure, aortic vasodilation, urinary protein concentration, fetal growth, and serum and placental cytokine levels. Pregnant rats treated with poly I:C displayed significantly elevated systolic blood pressures compared to pregnant rats and nonpregnant rats treated with poly I:C on day 18 of gestation. Poly I:C-treated pregnant rats also exhibited significantly decreased aortic vasodilation, significantly increased urinary protein concentrations, and had more malformed pups/litter. Additionally, poly I:C-treated rats exhibited a significant increase in placental TLR3 expression and proinflammatory/anti-inflammatory cytokine ratio compared to vehicle-treated rats. Poly I:C treatment of nonpregnant control rats had no effect on systolic blood pressure, aortic vasodilation, or urinary protein concentrations. These findings demonstrate that sustained maternal immune system activation via TLR3 during pregnancy causes PE-like symptoms in rats and suggest that viral infection during pregnancy may contribute to the development of PE.

Selenium and Vitamin E Modulates Radiation-Induced Liver Toxicity in Pregnant and Nonpregnant Rat: Effects of Colemanite and Hematite Shielding

The levels of liver lipid peroxidation, glutathione peroxidase, reduced glutathione, and vitamins A and E were used to follow the level of oxidative damage caused by ionizing radiation in pregnant rats. The possible protective effects of selenium and vitamin E supplemented to rats housed in concrete-protected cages using hematite and colemanite were tested and compared to untreated controls. Ninety-six rats were randomly divided into four main equal groups namely control (A), normal concrete (B), concrete containing colemanite (C), and concrete containing hematite (D). Except group A, all groups exposed to 7 Gy radiation. The four main groups were divided into four subgroups each as follows: subgroups 1 (n = 6): nonpregnant control rats. Subgroups 2 (n = 6): selenium and vitamin E combination was intraperitoneally (i.p.) given to the nonpregnant rats for 20 days. Subgroups 3 (n = 6): pregnant control rats. Subgroups 4 (n = 6): selenium and vitamin E combination was i.p. given to the pregnant rats for concessive 20 days. Lactate dehydrogenate, alkaline phosphates, and lipid peroxidation values were higher in subgroups 1 and 3 than in no radiation group although glutathione peroxidase and vitamin E levels in liver were lower in radiation group than in no radiation group. Lactate dehydrogenate activity and lipid peroxidation levels were found to be decreased in subgroups 2 and 4 protected with concrete containing hematite and colemanite when compared to subgroup 1 and 3 with normal concrete. The radiation doses in rats housed by concrete without colemanite and hematite exposed radiation clearly showed liver degeneration. In conclusion, selenium and vitamin E supplementations and housing by concrete with colemanite was found to offer protection against gamma-irradiation-induced liver damage and oxidative stress in rats, probably by exerting a protective effect against liver necrosis via its free radical scavenging and membrane stabilizing. Protective effects of colemanite in the liver seem to be more important than in hematite.

Low-Protein Diets Reduce PKAα Expression in Islets from Pregnant Rats

We investigated the effect of protein restriction on insulin secretion and the expression of protein kinase (PK)Aalpha and PKCalpha in islets from control and pregnant rats. Adult control nonpregnant (CN) and control pregnant (CP) rats were fed a normal-protein diet (17%), whereas low-protein nonpregnant (LPN) and low-protein pregnant (LPP) rats were fed a low-protein diet (6%) for 15 d. In the presence of 2.8 and 8.3 mmol glucose/L, insulin secretion by islets of CP rats was higher than that by islets of CN rats. Compared with the CN groups, insulin secretion by islets of LPN rats was lower with 8.3 but not with 2.8 mmol glucose/L. The insulin secretion by islets of LPP rats was higher than by LPN rats at both glucose concentrations. IBMX (1 mmol/L), a phosphodiesterase inhibitor, increased insulin secretion by islets from pregnant rats, and this effect was greater in islets of CP rats than in LPP rats. Forskolin (0.01-100 micromol/L), a stimulator of adenylyl cyclase, increased insulin secretion only in islets of CN and CP rats, with a higher 50% effective concentration in islets of CP rats compared with CN rats. The insulin secretion induced by phorbol 12-myristate 13-acetate (a stimulator of PKC) was higher in islets of LPN and LPP rats than in the respective controls, especially at 8.3 mmol glucose/L. PKAalpha, but not PKCalpha, expression was lower in islets of rats fed low protein than in the controls, regardless of the physiological status of the rats. All endocrine cells of the islets, including beta-cells, expressed the PKAalpha isoform. The cytoplasmic distribution of this enzyme in beta-cells was not modified by pregnancy and/or protein restriction. In conclusion, our results indicate that the response of islets from rats fed low protein during pregnancy is similar to that of control rats, at least for physiologic glucose concentration. However, the decreased response to IBMX and forskolin indicates decreased production and/or sensitivity to cAMP; this was associated with a decrease in PKA expression, which may result in lower PKA activity.

Effects of sex steroids on expression of adenylyl cyclase messenger RNA in rat uterus

The aim of our study was to investigate the effects of estradiol (E2) and/or progesterone (P4) bilateral ovariectomized rats on gene expressions of adenylyl cyclases (AC2, AC4, AC6, AC9). Non-pregnant (NP) Wister rats (between post-natal 10 and 12 weeks) and normal pregnant rats (between postnatal 10 and 14 weeks) were used. NP rats were divided into five groups: 1) control NP rats, 2) ovariectomy rats (OVX), 3) OVX injected with E2 (6 microg) for 4 days (E2), 4) OVX injected with P4 (5 mg) for 4 days (P4), 5) ovariectomy rats injected with E2 (6 microg) and P4 (5 mg) for 4 days (E2/P4). The ovariectomized rats were sacrificed by anesthesia of diethyl ether after 24 h from the last injection. The pregnant group was sacrificed in the same way on 14 (P14), 17 (P17) and 21 (P21) of pregnancy, because the days between P14 and P17 were the second trimester of pregnancy and P21 was the third trimester. Total RNA were prepared from the uteri of each subject, and expression of ACs was analyzed by reverse transcription-polymerase chain reaction (RT-PCR). Expression of mRNAs for AC2, AC4, AC6 and AC9 were maximally increased on P17 and then decreased on P21. In OVX rats, expression of mRNAs for AC2, AC4, and AC9 were decreased as compared to NP. AC2 mRNA was significantly increased by E2 treatment. AC4 and AC9 mRNA was significantly increased by injection of E2 or P4. AC6 mRNA level was not affected by E2 and/or P4. In conclusion, AC2, AC4 and AC9 gene expression is affected by estrogen and/or P4. On the contrary, AC6 gene expression was not changed by OVX or hormone treatment. Since, all ACs mRNA examined here are increased during pregnancy, AC6 may be affected by other factor(s) other than estrogen and P4.

Asymmetric dimethylarginine increases myogenic reactivity in mesenteric arteries of non-rupp rats when compared to rupp rats

MESENTERIC ARTERIES OF NON-RUPP RATS WHEN COMPARED TO RUPP RATS PAUL SPEER, ROLANDO RAMIREZ, JULIANNA MATTHEWS, JACQUELINE NOVAK, University of Pittsburgh, Obstetrics, Gynecology and Reproductive Sciences, Pittsburgh, Pennsylvania, University of Pittsburgh, Magee-Womens Research Institute, Pittsburgh, Pennsylvania OBJECTIVE: Asymmetric dimethylarginine (ADMA), an endogenous inhibitor of NOS, is increased in preeclamptic pregnancies. Increased ADMA has been linked to oxidative stress generated by reduced placental perfusion and may contribute to preeclampsia by decreasing NO synthesis. Myogenic reactivity is increased in mesenteric arteries in a rat model of reduced uterine perfusion pressure (RUPP). We hypothesized that, when exposed to ADMA, mesenteric arteries from pregnant non-RUPP (SHAM) rats, would exhibit increased myogenic reactivity similar to mesenteric arteries from pregnant RUPP rats. STUDY DESIGN: Mesenteric arteries (200-250 mm) were dissected from pregnant RUPP rats (n = 3), pregnant SHAM rats (surgical control, n = 2), and non-pregnant rats (n = 3) on day 20 of gestation. Myogenic reactivity was assessed using pressure arteriograph. Vessels were either pre-treated with ADMA 1mM or non-treated. After phenylephrine constriction intraluminal pressure was increased stepwise from 20-120 mm Hg. Myogenic responses were normalized as a % change in vessel diameter compared to the initial diameter at 20 mm Hg. Myogenic reactivity is greatest in arteries that demonstrate the smallest percent change in diameter with increasing pressure. Values expressed are mean % change. RESULTS: Arteries from the SHAM animals were less myogenic than arteries from the RUPP rats or nonpregnant controls. At 100 mm Hg, vessel diameter in the SHAM animals increased by 50% compared to only 22% in ADMA treated vessels. In arteries isolated from RUPP animals myogenic reactivity was increased compared to the SHAM animals and reactivity was not increased by ADMA treatment. ADMA had no effect on the arteries isolated from nonpregnant control rats. CONCLUSION: ADMA increases myogenic reactivity in pregnant SHAM rats but has little effect on pregnant RUPP rats. The increased myogenic reactivity observed in mesenteric arteries from RUPP rats may occur from NOS dysfunction independent of ADMA.

Decreased contraction-stimulated glucose transport in isolated epitrochlearis muscles of pregnant rats

Late pregnancy is characterized by insulin resistance for glucose transport in skeletal muscle. The main purpose of this study was to investigate the effect of late pregnancy on contraction-stimulated glucose transport in isolated rat skeletal muscle after in vitro electrical stimulation. Isolated epitrochlearis muscles of 19-day pregnant and aged-matched nonpregnant control rats were studied. One muscle from each rat was stimulated to contract, and the contralateral muscle served as a resting control. Tension developed during contractile activity, 3-O-methylglucose (3-MG) transport rate, and glycogen concentration were determined. Epitrochlearis muscles from other rats were used to measure insulin-stimulated 3-MG transport. There was no detectable difference between the nonpregnant and pregnant groups for contractile performance (peak tension, total tension, or fatigue). Pregnancy was not associated with significant changes in muscle glycogen concentration (resting or after contractile activity) or the contraction-stimulated decrement in glycogen concentration. For muscles from pregnant vs. nonpregnant groups, there was a 22% reduction (P < or = 0.05) in contraction-stimulated glucose transport, a 28% decrease (P < or = 0.05) in insulin-stimulated glucose transport, and unchanged basal glucose transport. In conclusion, isolated epitrochlearis muscles from pregnant vs. nonpregnant rats had a relative decrement in contraction-stimulated glucose transport that was similar to the relative decline in insulin-stimulated glucose transport. The decrement in contraction-stimulated glucose transport was not attributable to pregnancy-related changes in tension development or glycogen levels. The similar relative decline in insulin- and contraction-stimulated glucose transport raises the possibility that pregnancy impairs a distal process that is common to mechanisms whereby each stimulus activates glucose transport.

Effects of pregnancy on CYPs protein expression in rat liver

A body of evidence suggests that pregnancy may be responsible for the depression in the microsomal enzyme activity and the reduction in the total content of cytochrome P450 (CYP) in the rat liver. However, changes in expression of individual CYP isozyme remain poorly known. The current study was designed to examine the changes in CYPs protein expression in the liver of F344 rats in midpregnancy and late pregnancy by Western blot analysis and immunohistochemistry. Total nine antirat CYPs antibodies (CYP1A1, CYP2B1/CYP2B2, CYP2C6, CYP2C12, CYP2D1, CYP2D4, CYP2E1, CYP3A1, and CYP4A1) were used. In comparison with age-matched nonpregnant control rats, there were significant decreases in hepatic levels of CYP2B2, CYP2C6, and CYP4A1 in midpregnancy (day 13) and CYP2B2, CYP2C6, CYP4A1, CYP1A1, CYP2B1, and CYP2E1 in late pregnancy (day 19). The expression of CYP2C12, CYP2D1, and CYP 3A1 did not differ between nonpregnant and pregnant rats, and CYP2D4 was not detectable in microsomal proteins obtained from nonpregnant and pregnant rats at a protein loading of 20 μg total protein per lane. Immunohistochemistry showed that there were no differences in the distribution and degree of immunostainability for the abovementioned antibodies to nine CYPs between pregnant and nonpregnant rats.

Hexokinase II activity and messenger ribonucleic acid abundance in adipose tissue and skeletal muscle during pregnancy and lactation in rats

OBJECTIVE: Our purpose was to investigate the influence of pregnancy and lactation on hexokinase II activity and gene expression in adipose tissue and skeletal muscle of rats. STUDY DESIGN: Intraabdominal adipose tissue and femoral quadriceps muscle were removed from Sprague-Dawley rats at various times (6 to 10 animals per group) during pregnancy and lactation. Hexokinase II messenger ribonucleic acid was assayed by quantitative ribonuclease protection analysis, and hexokinase activity was measured with the glucose-6-phosphate–coupled assay. RESULTS: The amount of hexokinase II messenger ribonucleic acid in adipose tissue on day 20 of pregnancy was 55.4% ± 8.4% ( p < 0.01, unpaired Student t test) of the value for nonpregnant control rats; hexokinase II activity was also decreased in this tissue at this time (39.34 ± 3.05 vs 27.81 ± 3.61 mU · min –1 · mg protein –1, p < 0.05). Hexokinase II activity and messenger ribonucleic acid abundance in skeletal muscle were unaffected by pregnancy and lactation. CONCLUSION: Both hexokinase II messenger ribonucleic acid abundance and enzyme activity are reduced in adipose tissue of pregnant rats near term, possibly contributing to the insulin resistance associated with late pregnancy.(Am J Obstet Gynecol 1997;176:651-5.)

"In vivo" glutamic acid metabolism in late pregnant rats.

Glutamic acid metabolism in 24-hour starved 20-day pregnant and control non-pregnant rats, following intravenously administered [14C]-glutamic acid has been studied. The utilization of glutamate as a gluconeogenic precursor is not increased in late pregnancy under 24-hour starvation and it is regulated by the lower blood substrate availability. In addition, the steady state levels of glutamate, glutamine, aspartate, protein and glucose in blood, liver and skeletal muscle, together with tissue glycogen and lipids and metabolite composition pools, are given for both non-pregnant and pregnant rats.

Systemic hemodynamics and oxygen transport during pregnancy in chronically instrumented, conscious rats.

Knowledge about possible alterations in cardiac output (CO), total peripheral vascular resistance (TPVR), and their time course and magnitude of change is conspicuously lacking for the conscious gravid rat. Therefore, we assessed CO using Fick methodology in unrestrained, chronically instrumented, conscious rats. The rats were studied during early (day 7), mid (day 13), or late gestation (day 18) along with nonpregnant control rats matched with respect to age and days postsurgery. Significant differences between pregnant and nonpregnant rats were observed during midgestation, when CO was increased by 26 +/- 12% and TPVR was decreased by 23 +/- 9% in the pregnant animals. These changes were accompanied by a narrowed arterial-mixed venous oxygen content difference (AVD; P < 0.05 vs. nonpregnant). In late gravid rats, CO was higher than nonpregnant values by 49 +/- 8%, and TPVR was lower by 34 +/- 7% (both P < 0.05). Oxygen consumption and carbon dioxide production were significantly increased, and AVD further narrowed when compared with the nonpregnant control group. With the exception of absent chronic respiratory alkalosis in pregnant rats, we conclude that cardiovascular and respiratory changes in conscious, gravid rats and in pregnant women are comparable. We speculate that the ultimate purpose of many of these adaptations is to increase CO so that oxygen delivery and the supply of nutrients to the uteroplacental units are sufficient or more than sufficient to meet oxygen and nutrient demands. At midgestation, the rise in CO seems to anticipate the oxygen needs of the nascent uteroplacental units.

Expression of c-fos and c-myc genes in uterus and nonreproductive organs during the implantation period in the rat.

The c-fos and c-myc mRNA levels were investigated in the uterus and nonreproductive organs of rats during the implantation period (from day 5 to 7 of pregnancy). They were determined by densitometric analysis of slot blots and the mean values (n = 4) at a defined age of pregnancy were compared with those observed in nonpregnant control rats (NP group). No significant variations of c-fos level were observed in the liver and brain of pregnant rats. In the uterus, the c-fos level decreased, reached a minimum on day 6 (4-fold decrease compared with the NP group), and then increased. The c-fos level significantly increased in the kidney (2- and 2.5-fold on days 6 and 7), and in the lung (2.5-fold on day 7). The c-myc level did not significantly vary in the uterus, liver, and lung. It significantly increased in the kidney (3-fold on day 7) and in the brain (4.1-, 3.8-, and 6-fold, on days 5, 6, and 7). The changes in c-fos and (or) c-myc gene expression in the uterus and nonreproductive organs could be due to sexual steroids and (or) systemic factors from uterine cells or blastocysts.

The effects of pregnancy and fluoride on orthodontic tooth movements in rats

The present investigation was undertaken in order to study the velocity of orthodontic tooth movement in rats and the effect of the hormonal changes that occur during pregnancy or with fluoride, which is one of several trace elements that affect hard tissue metabolism. Adult, female Sprague-Dawley rats were separated into three groups: non-pregnant, pregnant, and non-pregnant NaF-supplied. All rats were treated with a fixed orthodontic appliance which moved the upper first molars in a buccal direction during 21 days. The appliances delivered an initial force of 150 mN. Repeated intra-oral, standardized radiographs were taken during the experimental period, and at the end of the experiment the maxillae were examined histologically. The velocity of tooth movement was calculated after measurement of the radiographs. The first molars were moved in a buccal direction in all groups. The mean value of the expansion from day 0 to 21 was significantly higher among the pregnant rats (0.64 mm) compared to the non-pregnant, control animals (0.46 mm) while the NaF-supplied rats had a significantly lower expansion (0.22 mm) compared to the control animals. In the histological examination of the pressure sides of the PDL of the upper first molars, the mean value of osteoclasts per microns x 10(-3) increased non-significantly in the group of pregnant rats and decreased significantly among the NaF-supplied animals compared to the non-pregnant control rats. The present experiment in rats indicated that the velocity of orthodontic tooth movement is influenced by hormones as well as trace elements.

Effect of pregnancy on the disposition of valproate in rats.

The disposition of sodium valproate in pregnant rats was studied comparing with nonpregnant (control) rats. In the pregnant rats, the total plasma clearance decreased significantly (p less than 0.05) from 7.06 ml/min/kg of the control to 5.34 ml/min/kg, whereas the plasma elimination half-life of valproate did not change. The serum unbound fraction (fs) of pregnant rats increased remarkably. The fs of the fetal plasma was lower than that of the maternal serum in spite of the lower albumin (main binding protein for valproate) concentration in the fetal plasma. A non-linear serum (plasma) protein binding was observed both in the control and the fetal rats, but not observed in the pregnant rats. In the pregnant rats, the tissue-to-plasma concentration ratio (Kp) of the brain was higher than that in the control rats, whereas the Kp values of the liver and and lung were lower than those in the control rats. In other tissues, the Kp values did not show a significant difference. Rapid placental transfer was observed and the Kp value of the fetus was 0.43.

Vitamin B-6 Metabolism in the Pregnant Rat: Effect of Progesterone on the (Re)Distribution in Maternal Vitamin B-6 Stores

Parameters of vitamin B-6 metabolism were studied in pregnant rats, nonpregnant control rats and progesterone- supplemented ovariectomized rats. Plasma pyridoxal 5′-phosphate (PLP) and pyridoxal concentrations in pregnant rats were 20 and 40% of those of nonpregnant rats, respectively. Excretion of 4-pyridoxic acid in the urine in pregnant rats was about 40% of that of nonpregnant rats. Liver PLP content was also lower during pregnancy, but liver pyridoxamine 5′-phosphate (PMP), kidney PLP and PMP and muscle PLP contents did not change significantly. Progesterone administration to ovariectomized rats resulted in slightly lower plasma, liver and kidney PLP levels than in intact untreated control rats. Liver and kidney pyridoxal kinase (PK) and pyridoxamine 5′-phosphate oxidase activities were similar in pregnant and nonpregnant rats. Progesterone treatment resulted in a significantly lower PK activity in the kidney of the treated rats than in untreated controls. It is concluded that the pregnancy-induced changes in vitamin B-6 metabolism were unlikely to be related directly to progesterone. However, progesterone may secondarily affect maternal vitamin B-6 stores during pregnancy, by temporary deposition and increased retention of vitamin B-6.

Protective effect of pregnancy against transplantation of lymphoma in rats.

Pregnancy was considered to aggravate concomitant neoplasia; however, recent observations in humans and experimental animals suggest that on the contrary tumor growth may be unfavorably affected by pregnancy. For this relationship to be investigated, a serially transplantable virus-induced lymphoma was inoculated into female rats of two different strains (WF and SD) in early or in late pregnancy. While all nonpregnant control rats died with lymphoma in 8-10 weeks, 36-75% of rats inoculated with lymphoma cells in the 1st week of pregnancy remained free of tumors, and 20-54% had tumors half the size of those in controls. When lymphoma cells were inoculated in the last week of pregnancy, the protective effect of pregnancy, although less clearly manifested, still resulted in 11% rats free of tumors and 78-91% rats with tumors markedly smaller than those of controls. Nonpregnant rats receiving pregnant rat serum in twice weekly injections grew tumors only 25-60% the size of those in rats receiving sera of nonpregnant rats. In vitro, pregnant rat sera added to the tissue culture media of rat lymphoma (AS line) or human leukemia (MOLT-4) cells resulted in reductions of viable target cells of 67-71%, respectively. The present experiments show that transplanted lymphoma cells that are 100% lethal in nonpregnant rats were totally or partially inhibited in their growth when the recipients were pregnant. Similar inhibiting effects were observed when pregnant rat serum was administered to lymphoma cells in vivo and in vitro. The protective effect against tumor growth was greater during early pregnancy, less accentuated during late pregnancy, and ceased entirely post partum and particularly during lactation, when tumor growth resumed on an accelerated course.

Hepatic extraction of endogenous inhibitors of drug binding to serum protein in the pregnant rat

Significant decreases in the serum protein binding of a fluorescent dye, 1-anilino-8-naphthalenesulfonate (ANS), and salicylic acid (SA) were observed in pregnant rats compared to that in nonpregnant (control) rats. A significant difference in the serum protein binding of ANS and SA between serum samples taken at the hepatic vein and portal vein or femoral artery was also observed in the pregnant rats, while such a sampling site difference in the serum protein binding was not observed in the control rats. In the pregnant rats the affinity of ANS binding to the primary binding site in the serum from the hepatic vein was approximately 70% higher than that in the case of serum from the portal vein. The hepatic extraction of nonesterified fatty acids (NEFA) was also determined, and the extraction ratios in the control and pregnant rats were 0.55 and 0.31 respectively. We concluded from these findings and other evidence that certain endogenous inhibitors of drug binding to serum protein (such as NEFA), which increase during pregnancy, were extracted efficiently by the liver and that the difference in the serum protein binding of ANS and SA between serum samples taken at the hepatic and portal veins or femoral artery in the pregnant rats may be explained by the hepatic extraction of endogenous inhibitors. Our present results support the previous finding by Chou et al. [ Int. J. Pharm. 18, 217 (1984)] that in pregnant rats the serum protein binding of phenytoin is greater in the hepatic vein than that in the femoral vein.

Calcium flux in vivo in the rat duodenum and ileum during pregnancy and lactation.

Intestinal calcium transport was examined in nonpregnant, pregnant, lactating, and 100 ng 1,25-dihydroxyvitamin D3-dosed rats. Solutions containing 150 mM NaCl, 1 mM Ca, and 0.1 microCi 45Ca were recirculated in vivo through the duodenum and ileum to determine calcium efflux from the lumen, influx into the lumen, and net absorption. In the duodenum of the nonpregnant control rats, efflux of calcium was greater than influx, resulting in net absorption of calcium. In the ileum, calcium efflux and influx were equivalent and there was little net movement of calcium. 1,25-Dihydroxyvitamin D3 [1,25(OH)2D3] significantly increased efflux and net absorption of calcium in the duodenum without affecting influx. In the ileum 1,25(OH)2D3 had no effect on calcium flux. During pregnancy and lactation there was a marked increase in mucosal tissue, and expression of transport data per centimeter of intestine gave different results than transport expressed per gram of dry mucosal tissue. Per centimeter of intestine, duodenal efflux and net absorption, but not influx, increased significantly during pregnancy and to greater extent during lactation. Per gram of dry mucosa, duodenal efflux and net absorption were increased significantly only during lactation, and the increase was comparable with that observed in 1,25(OH)2D3-dosed rats. In the ileum of pregnant and lactating rats, efflux and influx expressed per centimeter of intestine increased to approximately the same extent, and net movement of calcium remained unchanged from the control level. Expression of ileal transport data per gram of dry mucosa resulted in no significant difference in calcium movement during pregnancy and lactation.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of pregnancy and diabetes on myofibrillar protease activity in maternal and fetal muscles.

The activity of protease was investigated by cleavage of 14C-labelled globin by the isolated myofibrillar fraction of maternal and fetal muscles of nonpregnant, pregnant, and pregnant diabetic rats, on days 15 and 20 of pregnancy. Diabetes was produced by i.p. streptozotocin injection on day 5 or 12 of pregnancy. There was no change in muscle protease activity on day 15 of pregnancy in nondiabetic rats, compared to nonpregnant control rats, whereas on day 20 protease activity rose in the gastrocnemius by 25%, in the diaphragm by 30%, and only slightly in the heart. Diabetes, imposed during days 12-20 of pregnancy, induced a further increase in protease activity in the gastrocnemius (42%), diaphragm (47%), and heart (25%). In rats with diabetes lasting from day 5 to 20 of gestation there were only slight further increases in protease activity. In contrast, maternal diabetes did not induce changes in myofibrillar protease activity of fetal leg or heart muscles compared with the corresponding muscles of fetuses of nondiabetic rats. The increased protease activity on the maternal side occurred at low insulin levels and/or reduced insulin sensitivity, whereas the absence of changes in protease activity on the fetal side was associated with sustained or even increased presence of insulin. This suggests that the adaptive changes in protease activity, in both pregnancy and superimposed diabetes, are related to insulin availability and its effectiveness.