Simultaneous Blood Samples Research Articles

The metabolic and endocrine milieu of the human fetus and mother at 18-21 weeks of gestation. I. Plasma amino acid concentrations.

Plasma levels of 17 amino acids were measured in 10 conscious mothers and their minimally stressed fetuses (mean body weight 302 g) at 18-21 wk gestation. Simultaneous blood samples were taken from the maternal antecubital vein, and from the fetal umbilical vein and artery by fetoscopy prior to termination of pregnancy. The mean concentrations of all amino acids were significantly higher in the fetal (2.26 mmol/liter) than in the maternal (0.96 mmol/liter) circulation, the total molar concentration of amino acids was 2.4 times greater in fetal than in maternal plasma. There was a significant positive relationship between maternal and fetal levels for most amino acids; the mean umbilical concentration difference was significantly positive for glycine, alanine, isoleucine, leucine, phenylalanine, and histidine.

Relationship of 15-keto-13,14-dihydro-prostaglandin F2 alpha concentrations in peripheral plasma with local uterine production of F series prostaglandins and changes in uterine blood flow during the early postpartum period of cattle.

Cows were prepared for surgery, either within 12 h after parturition (Day 0, n = 3), on Day 1 (n = 1) or on Day 2 (n = 1) postpartum. The previously gravid uterine horn was exposed through a high lumbar laparotomy, and catheters inserted into an uterine branch of the ovarian vein (UBOV) and in the main uterine artery (UA) via a branch of the main uterine artery. A blood flow transducer (8-13 mm, internal diameter) was placed around the UA. Starting 12-24 h following surgery, simultaneous blood samples were collected from UBOV and UA at 15-min intervals for 1 or 2 h daily from Days 1 to 10 postpartum (mean = 5.3 days). Concurrently, uterine blood flow (UBF) was recorded daily for 6 h. Mean concentrations of prostaglandin F2 alpha (PGF2 alpha) and 15-keto-13, 14-dihydro-PGF2 alpha (PGFM) were higher (P less than 0.01) in UBOV than UA (4.64 +/- 0.6, n = 96 vs. 0.08 +/- 0.02 ng/ml, n = 92 and 5.67 +/- 0.41, n = 98 vs. 1.02 +/- 0.09, n = 94, ng/ml, respectively). Concentrations of PGF2 alpha and PGFM in the UBOV increased (P less than 0.1) on Days 2 and 3 and decreased (P less than 0.01) thereafter. Mean UBF (ml/min) decreased (P less than 0.01) from 3079 +/- 683 on Day 1 to 602 +/- 56 on Day 2 and was 413 +/- 55 on Day 5.(ABSTRACT TRUNCATED AT 250 WORDS)

Circulating free fatty acids, insulin, and glucose during chemical stimulation of hypothalamus in rats.

The aim of this study was to investigate plasma free fatty acids (FFA), insulin, and blood glucose during chemical stimulation of the lateral and ventromedial hypothalamic areas (LHA and VMH) in rats. Therefore male Wistar rats were implanted with bilateral cannulas in the LHA or the VMH and into the left and right jugular veins. Freely moving rats were then infused into the LHA and VMH with norepinephrine (NE), epinephrine (E), or acetylcholine or intravenously with NE or E. Before, during, and after the infusions, simultaneous blood samples were taken without disturbing the animals. Infusion of NE into the LHA resulted in a decrease of plasma FFA and a simultaneous increase of insulin. NE infusion in the VMH elicited an increase of plasma FFA, plasma insulin, and blood glucose. E infusion into the LHA did not lead to a change of plasma FFA, whereas insulin and glucose showed an increase. E infusion into the VMH evoked increases of plasma FFA and insulin. Peripheral administration of NE led to a sharp increase of FFA, whereas plasma insulin and blood glucose did not change. E in the periphery elicited an augmentation of plasma FFA and blood glucose and a suppression of insulin during infusion. After termination of E infusion, plasma FFA and glucose levels decreased, whereas plasma insulin showed a sharp increase.(ABSTRACT TRUNCATED AT 250 WORDS)

Role of spontaneous portal-systemic shunting in hyperinsulinism of cirrhosis

The possible contribution of hepatocellular damage and portal-systemic shunting to hyperinsulinism in cirrhosis was studied in 23 cirrhotics, 8 of whom had a surgical portacaval shunt, and 16 controls by measuring insulin and the connecting peptide (C-peptide) concentrations in simultaneous samples of peripheral arterial and hepatic venous blood. The fractional hepatic insulin extraction (0.48 +/- 0.06, mean +/- SE) was normal in cirrhosis. The hepatic insulin elimination rate was directly related to arterial insulin levels (r = 0.91, P less than 0.001) even at very high circulating levels. Extrahepatic insulin metabolism was measured across the kidney and lower limb. There were no significant differences between cirrhotics and control subjects in relation to renal (0.25 +/- 0.05 vs. 0.23 +/- 0.04) and lower limb insulin extraction (0.14 +/- 0.07 vs. 0.19 +/- 0.04). While in the control group hepatic venous insulin (0.143 +/- 0.018 pmol/ml) markedly exceeded the peripheral insulin concentration (0.083 +/- 0.009 pmol/ml, P less than 0.01), the contrary was found in cirrhotics with end-to-side portacaval shunt in whom all the pancreatic venous effluent is shunted to the systemic circulation (hepatic venous insulin, 0.130 +/- 0.028 pmol/ml; peripheral, 0.234 +/- 0.037 pmol/ml; P less than 0.01). Portal-hypertensive cirrhotics without a surgical portacaval shunt also had hepatic venous insulin levels (0.132 +/- 0.029 pmol/ml) below peripheral arterial insulin concentrations (0.205 +/- 0.041 pmol/ml, P less than 0.01). The study suggests that hyperinsulinism in cirrhosis is not the result of an intrinsic defect of hepatic insulin metabolism but of the spontaneous shunting of portal blood to the systemic circulation.

Absorption of the cerebrospinal fluid and intracranial compliance in an amphibian, Rana pipiens.

Experiments have been carried out to investigate the absorption of the cerebrospinal fluid (c.s.f.) and the intracranial compliance in an amphibian, Rana pipiens, using infusions into the c.s.f. system through glass micropipettes. Resistance to absorption of the c.s.f. was estimated by the constant rate infusion technique. Mean absorption resistance for infusions of artificial c.s.f. into the lateral ventricles and into the cerebral subarachnoid space were 15.48 and 16.52 mmH2O min microliter-1 respectively. This difference was not significant and it is concluded that the pores in the posterior tela situated in the roof of the fourth ventricle do not offer any resistance to the flow of c.s.f. out of the ventricles. The resistance to drainage of the c.s.f. in this amphibian is higher than that found for mammals. Mean resting c.s.f. pressure, estimated from the intercept of the regression line with the pressure axis at zero infusion rate was 18.0 mmH2O. Absorption resistance was measured from the cerebral subarachnoid space before and after injection of 4 microliter Indian ink solution. There was a 3-fold increase in resistance following ink injection. Two-way analysis of variance showed the difference to be significant (P less than 0.01) suggesting that the outflow sites can become partially blocked by particulate matter. During a continuous 3 h infusion of artificial c.s.f. containing [14C]dextran or [125I]-labelled human serum albumin (RISA) into the lateral ventricles, the mean percentage uptakes into the systemic circulation after the first 0.5 h of a 3 h period were 74.1 and 61.9% respectively. The difference is not significant. The rapid and high uptake into blood suggests there is a direct communication between c.s.f. and blood in amphibians. During continuous infusion of RISA into the lateral ventricles, simultaneous blood samples were taken from the femoral artery and the internal dorsal vertebral vein. Radioactivity was found to be 13.2% higher in venous samples. This suggests that at least some c.s.f. drainage takes place directly into the spinal venous system. Intracranial compliance was investigated by recording the peak pressure in response to a series of bolus injections of artificial c.s.f. into one lateral ventricle. Compliance was estimated to be 0.11, 0.10 and 0.09 microliter mmH2O-1 for injection rates of 12.74, 16.62 and 25.10 microliters min-1 respectively. The difference between these values is not significant. The results suggest that for injection volumes over 5 microliters the c.s.f. system behaves elastically.

Hypothalamically-induced insulin release and its potentiation during oral and intravenous glucose loads

Male Wistar rats were provided with bilateral cannulas in the lateral hypothalamic area (LHA) and cannulas in the left and right jugular vein. Freely moving rats provided in this way with cannulas were infused with transmitters in the LHA and with various substances in the blood circulation during simultaneous sampling of blood without disturbing the animals. Infusion of norepinephrine (NE) in the LHA resulted in increased insulin levels while plasma glucagon and blood glucose were nearly not affected. This LHA mediated insulin release was suppressed by atropine injection in the blood circulation suggesting a vagal contribution to the observed phenomenon. Administration of either an oral or i.v. glucose load during noradrenergic stimulation of the LHA elicited an exaggerated insulin response when compared to their controls. This LHA potentiated insulin response during an oral and i.v. glucose load could be suppressed by atropinization of the rats. It is concluded that meal-related stimuli are relayed to the NE-stimulated area of the LHA and that these stimuli modulate the output from this area of the LHA that is concerned with the release of insulin.

Aromatization by splanchnic tissue in men.

To measure the rate of aromatization that occurs in splanchnic tissue, four men with normal liver function were infused through an arm vein with [3H]androstenedione/[14C] estrone and four men were infused with [3H]testosterone/[14C] estradiol before indicated cardiac procedures. Catheters were placed under fluoroscopic control in the hepatic vein and descending aorta. Simultaneous blood samples were then obtained from the aorta and the hepatic vein after 90 and 120 min of infusion. The samples were analyzed for radioactivity after multiple chromatographic purification steps. The MCRs, overall aromatization (fraction of androgen infused measured as estrogen in arterial blood), splanchnic extractions, and splanchnic aromatization (fraction of androgen entering the splanchnic tissue which leaves as estrogen) were determined. The mean values for MCRs of androgens and estrogens and overall aromatization for androstenedione and testosterone were similar to those reported previously. The splanchnic extraction values of androstenedione, testosterone, estrone, and estradiol were 0.57 +/- 0.10 (+/- SE), 0.39 +/- 0.12, 0.60 +/- 0.09, and 0.64 +/- 0.18, respectively. The mean splanchnic aromatization of androstenedione to estrone was 0.00086 +/- 0.00072, and the mean splanchnic aromatization of testosterone to estradiol was 0.00059 +/- 0.00020. If one assumes that the splanchnic bed receives 20% of the cardiac output, then the splanchnic bed is responsible for less than 4% of the overall peripheral aromatization of androstenedione or testosterone.

Dynamic fluctuations in blood and spleen radioactivity: Splenic contraction and relation to clinical radionuclide volume calculations

Alterations in the blood radioactivity affect ventricular volume calculations using count-based radionuclide ventriculography. To study this phenomenon, the effect of time, posture and supine exercise on blood radioactivity, red blood cell count and splenic radioactivity was evaluated. The red blood cell count, and blood, splanchnic and splenic radioactivity remained stable in five patients studied at rest in the supine position. On standing, blood radioactivity increased 10 +/- 3% (standard error of the mean), and abdominal radioactivity decreased 14.5 +/- 6.5% (both p less than 0.05). In 10 patients, splenic radioactivity decreased after supine exercise by 49 +/- 7%, while blood radioactivity increased 10.5 +/- 1.5% and red blood cell count increased 7.5 +/- 1.5% (all p less than 0.001). Splenic radioactivity increased gradually after exercise and decreased after a second exercise period. In the exercising patients, blood radioactivity increased by 14.5% and correlated with an increase in the red blood cell count (r = 0.57, p = 0.01, 19 samples from 10 patients). Reduction in splenic radioactivity also correlated with the increase in red blood cell count (r = -0.51, p = 0.025). The data demonstrate splenic shrinkage in human beings and an inverse relation between changes in splenic and blood radioactivity. These dynamic fluctuations emphasize the need for simultaneous blood sampling for accurate calculation of left ventricular volume and high-light the importance of regional volume shifts during exercise.

CEFTRIAXONE (CTX) KINETICS AND CEREBROSPINAL FLUID (CSF) CONCENTRATIONS IN INFANTS AFTER LOADING (LD) AND MAINTENANCE DOSES (MD)

Thirteen infants (0.4-1.4 yrs) with meningitis were studied. CTX therapy consisted of a 75 mg/kg LD, followed by 50 mg/kg MD every 12 hrs IV over 10 minutes. Simultaneous blood and CSF samples were obtained in 11 infants at 11.5-12.8 hr after LD. In 3 of these, multiple blood samples were collected after the LD and after 9-10 days of MD; simultaneous blood and CSF samples were also collected at 1.25-5.75 hr at steady-state. CTX was measured by HPLC. Simultaneous serum and CSF concentration ranged from 10.5-40.3 and 1.8-8.0 μg/ml after the loading dose and 74-139 and 5.8-7.9 μg/ml at steady-state, respectively. After LD and at steady-state, CTX total clearance was 1.06±0.18 and 0.64±0.06 ml/min/kg (P<0.05), distribution volume was 0.33±0.06 and 0.26±0.06 L/kg and elimination half-life was 3.67±0.06 and 4.61±0.28 hr, respectively. A higher CTX clearance at higher dose may be partly due to concentration-dependent plasma protein binding of CTX reported in adults. Although the CSF/serum concentration was low, the CSF bactericidal titers exceeded 1:512 suggesting a great potential for CTX therapy of central nervous system infections due to susceptible organisms.

Effect of pulmonary blood flow on leukocyte uptake and release by dog lung.

The effect of pulmonary blood flow on leukocyte uptake and release by the lung was examined in 10 anesthetized spontaneously breathing dogs. Pulmonary arterial and pulmonary venous blood was sampled with catheters placed into the right ventricle and aorta, respectively. Pulmonary blood flow was lowered by inflating a balloon catheter located in the inferior vena cava. In five experiments simultaneous blood samples were drawn from the right ventricle and aorta at 10-s intervals during a control period, a 2- to 3-min period of low flow, and a recovery period. In five additional experiments, less frequent samples were taken over periods of 15-60 min. Total leukocyte concentrations and differential counts were determined for each blood sample. The study shows that large numbers of leukocytes become sequestered within the lung when pulmonary blood flow is low and that an equivalent number of cells are released from the lung after deflation of the balloon catheter. Both the polymorphonuclear leukocytes and the lymphocytes were taken up by the lung when pulmonary blood flow was reduced. We conclude that pulmonary blood flow has a marked effect on the uptake and release of leukocytes by the dog lung.

Penetration of cefsulodin into bronchial secretions.

The objective of this study was to evaluate the penetration of cefsulodin, a new cephalosporin active against Pseudomonas aeruginosa, into the bronchial secretions. The study was carried out in 28 patients with respiratory infections; 11 patients received a single dose of 1 g i.v. (bolus); 17 patients received multiple doses of 1 g every 8 h for 48 h. Simultaneous samples of blood and bronchial secretions were collected 30 min and 1, 2, 4 and 6 h after injection. Bronchial secretions were obtained from 23 patients by means of fiberoptic bronchoscopy and in 5 tracheostomized patients (with severe respiratory insufficiency) through a tracheostomy cannula. The assays of cefsulodin were performed by means of the microbiological agar diffusion technique. The results of the study showed a noticeable penetration of the drug into the bronchial secretions, with a mean peak reaching 3.1-5.3 micrograms/ml at the 3rd or 4th hour, a slow elimination and residual levels at 6 h ranging between 2.0 and 6.0 micrograms/ml. The rate of penetration was not influenced by the administration of multiple doses of the drug. The ratios between bronchial concentrations and simultaneous serum concentrations ranged between 10 and 30%, corresponding to the usual values found for other cephalosporins. In conclusion, this study provides satisfactory results and confirms the presence of bronchial levels capable of inhibiting P. aeruginosa.

Vasopressin in blood and third ventricle CSF during dehydration, thirst, and hemorrhage.

Samples of cerebrospinal fluid (CSF) were collected from the anterior part of the third cerebral ventricle of mongrel dogs with a chronically implanted device. Repeated experiments with simultaneous sampling of CSF and venous blood in 60- to 90-min intervals were performed in conscious dogs after 24-h water deprivation and during subsequent rehydration by drinking, during thirst stimulation by intravenous infusion of 5% saline, and during blood removal (12 ml X kg body wt-1). The CSF and plasma samples were analyzed for osmolality and arginine vasopressin (AVP) with a radioimmunoassay. Compared with normally hydrated dogs, 24-h water deprivation caused plasma AVP to rise significantly from 2.5 to 7.7 pg X ml-1 and CSF AVP from 24.2 to 31.3 pg X ml-1. Subsequent drinking significantly reduced plasma and CSF AVP. Thirst stimulation by hypertonic infusions was associated with rises of plasma and CSF AVP. Modest reduction of blood volume also increased both plasma and CSF AVP. Plasma AVP in each of the described physiological disturbances of salt or fluid balance was positively correlated with CSF AVP.

Sampling and analysis of cerebrospinal fluid for chronic studies in awake rats

A method is described whereby cerebrospinal fluid (CSF) may be sampled repeatedly from awake rats over a period of 1 to 10 wk. Stainless steel or Teflon catheters (22-gauge) were implanted in the cisterna magna of anesthetized rats (n = 19) via a midline hole immediately rostral to the interparietal-occipital suture. Several days later almost simultaneous CSF and blood samples from the same air-breathing animals were slowly drawn into glass capillary tubes. pH was determined immediately by electrode and total CO2 by microgasometer. Because sampling via Tygon microbore tubing attached to the implanted catheters allowed part of CSF CO2 content to be lost through the tube wall, stainless steel tube is preferred to make this connection. For mock CSF, total CO2 calculated from pH and PCO2 values was closely comparable to that directly measured by microgasometer. CSF pH, PCO2, and [HCO-3] in five awake rats were found to be similar to those reported in the literature for the briefly anesthetized rat. The sampling procedure did not of itself significantly alter breathing patterns (n = 14). Thus, chronic CSF sampling is feasible in awake rats for purposes of studies of ventilatory control.

INFLUENCE OF SAMPLE SITE ON BLOOD CONCENTRATIONS OF ICI 35 868

Simultaneous blood samples from an artery, a peripheral vein and a central vein were analysed for ICI 35868 concentrations following an induction dose of 2.0 mg kg-1 administered i.v. over 60 s, to five patients before cardiac surgery. Up to 60 s after the end of the administration of the drug there were wide differences in drug concentration between the sampling sites. Thus, any attempt to correlate effect with blood concentration over this early period would be problematic. From 60 s there were no significant differences in drug concentration between the three sites. Thus, as long as the mixing period is allowed for, peripheral venous sampling provides an acceptable alternative to arterial puncture in studies to correlate drug effect and concentration and for pharmacokinetic investigations.

Lactate and Proton Dynamics in the Rainbow Trout (Salmo Gairdneri)

ABSTRACT Chronically cannulated rainbow trout were subjected to 6 min of severe burst exercise and monitored over a 12 h recovery period. There were short-lived increases in haematocrit, haemoglobin, plasma protein, Na+ and Cl− levels. Plasma [Cl−] later declined below normal as organic anions accumulated. A much larger and more prolonged elevation in plasma [K+] probably resulted from intracellular acidosis. An intense extracellular acidosis was initially of equal respiratory (i.e. ) and metabolic (i.e. ) origin. However was rapidly corrected while the metabolic component persisted. Plasma ammonia increases had negligible influence on acid-base status. Elevations in blood lactate (ΔLa−) were equal to immediately post-exercise but later rose to twice the latter. Simultaneous white muscle biopsies and blood samples demonstrated that muscle to blood gradients of lactate and pyruvate were maximal immediately post-exercise. As blood levels rose and muscle levels declined, an approximate equilibrium was reached after 4 h of recovery. Intra-arterial infusions of lactic acid in resting trout produced a severe but rapidly corrected metabolic acidosis. The rates of disappearance of and ΔLa− from the blood were equal. Infusions of similar amounts of sodium lactate produced a small, prolonged metabolic alkalosis with a much slower ΔLa− disappearance rate. It is suggested that the excess of ΔLa− over in the blood after exercise is associated with differential release rates of the two species from white muscle rather than differential removal rates from the bloodstream, and that the majority of the lactic acid load in muscle is removed by metabolism in situ.

Quantitative description of whole blood CO 2 dissociation curve and Haldane effect

A simple procedure is presented to describe accurately the whole blood CO 2 dissociation curve on linear content (C CO 2 ) and pressure (P CO 2 ) coordinates with an exponential equation (C CO 2 = K·P CO 2 b). A single coordinated and the hemoglobin concentration, Hb, are required. Whole blood C CO 2 can be calculated from values for pH, P CO 2 , Hb and O 2 saturation by empirically accurate equations. The mathematical description of the CO 2 curve was employed to quantitate the in vivo Haldane factor (f H) from simultaneous arterial and mixed venous blood samples in 20 healthy exercising subjects. The mean ± SE was 0.28 ± 0.03 (vol. % ΔC CO 2 /vol. % δHbO 2). In 20 patients with severe obstructive lung disease f H was 0.29 ± 0.08 when calculated from arterial samples while breathing air and 100% O 2. Values for f H were not related significantly to acid-base status or Hb as suggested by previous workers. By assuming these or other values for f H, the in vivo change in blood P CO 2 resulting from a given change in oxygenation can be predicted.

Blood and milk concentrations of metronidazole in mothers and infants.

In order to assess the amounts of metronidazole and its clearance in suckling neonates whose mothers received the drug in therapeutic doses, we measured its levels in maternal plasma and milk and in infant plasma. Eleven mothers receiving 600 mg metronidazole daily and 4 receiving 1200 mg and their 15 infants had milk and plasma levels determined with a specific semi-micro high-pressure liquid chromatographic method. Maternal mean plasma levels were 5.0 micrograms/ml, range 1.0 - 11.6 micrograms/ml (600 mg/day) and 12.5 micrograms/ml range 3.7 - 17.9 micrograms/ml (1200 mg/day) and corresponding infant plasma levels were 0.8 micrograms/ml, range 0.3 - 1.4 micrograms/ml and 2.4 micrograms/ml, range 0.6 - 4.9 micrograms/ml. Maternal milk/plasma ratio was 1 and baby/mother plasma ratio was 0.15, independent of dosage (Tab. I). The levels of metronidazole hydroxy metabolite (I) were all below those of metronidazole (Tab. II). Simultaneous milk and blood samples showed almost identical levels (Tab. III). Infant total clearance of metronidazole was calculated to be ca. 60% of maternal clearance by body weight and 24% by body surface, independent of dosage, while maximum infant metronidazole intake was estimated to be 3.0 mg/kg/day assuming a daily intake of 500 ml milk. It is recommended to avoid simultaneous breastfeeding and metronidazole therapy until possible harmful longterm effects on the neonates are known.

Antipyrine and Acetaminophen Kinetics in the Rat: Comparison of Data Based on Blood Samples from the Cut Tail and a Cannulated Femoral Artery

Antipyrine and acetaminophen kinetics were determined from concentration data obtained by simultaneous blood sampling from the cut end of the tail and a cannulated femoral artery in the rat. Significant differences in concentrations and kinetics for both drugs were found by comparison of the two sampling sites. The hypothesis that the differences were due to a low tail blood flow was tested. The tail blood flow was measured with a microsphere technique, and tail antipyrine concentrations were calculated from the relationship between arterial antipyrine concentration, tail flow, and time for comparison with the observed antipyrine concentrations. Mean blood flow of the rat tail was 0.02ml/min/ml tail tissue at 22°, which was 8.8 and 0.9% of the liver and kidney flow, respectively. Tail flow increased more than twofold by elevation of the tail temperature to 37°. The calculated tail antipyrine concentration versus time curve showed a very close correspondence to the observed antipyrine tail concentration versus time curves. The results show that tail flow is a major determinant of antipyrine tail concentration in the rat. Kinetic data based on blood samples from the cut end of the tail, therefore, should be interpreted with caution.

The effect of temporary venous occlusion on trace mineral concentrations in plasma

The effects of short-term venous occlusion on plasma concentration of trace mineralszinc, iron, and copperwere studied in normal volunteers. In one experiment, antecu-bital vein blood samples were drawn simultaneously from both arms of 14 subjects while their left arms remained free and their right arms had been occluded from 60 s at 40 mm Hg pressure. Statistical comparison of paired samples showed a significant increase in zinc (p < 0.05) and iron (p < 0.001), but not copper concentrations in plasma from the occluded extremity. The mean increase in concentration in the right (ligated) arms with respect to the left (unligated) arms was 3.7 and 24.6%, for zinc and iron, respectively. In a second experiment, simultaneous blood samples were drawn from five subjects with neither arm occluded. No significant difference between right and left was observed. Thus, application of tourniquets during the sampling of venous blood for trace mineral analysis introduces a nonrandom factor. Standardization of sampling techniques is essential to overall reliability of trace mineral determinations.

The relationship between blood and cerebrospinal fluid prolactin in nonhuman primates

We studied the relationship between plasma and cerebrospinal fluid (CSF) concentrations of prolactin (PRL) in repeated and simultaneous samples of blood and CSF from chair-restrained rhesus monkeys. Following administration of thyrotropin releasing hormone (TRH), each of 4 monkeys showed increased plasma and lumbar CSF PRL concentrations. Increases in CSF PRL concentrations were muted and delayed until 60 min after peak plasma concentrations were attained. In 3 other monkeys we compared PRL concentrations in simultaneous lateral ventricular and lumbar CSF samples. Although we found no difference in PRL concentrations under baseline conditions, a ventricular-lumbar PRL concentration gradient became apparent after TRH stimulation. These studies demonstrate that changes in plasma PRL concentrations are reflected in CSF concentrations. They suggest that a significant blood-CSF barrier exists for PRL and that PRL may enter the the CSF selectively via the ventricles.