Ringer Bicarbonate Research Articles

Hypocalcemia-associated modulation of renal response to acute volume expansion in rats.

The present study used free-flow micropuncture and whole-kidney clearance studies to determine the renal response to normocalcemic vs. hypocalcemic acute volume expansion (AVE) in anesthetized Munich-Wistar rats. Animals received AVE with Ringer bicarbonate to 10% body weight; half of these animals were supplemented with calcium to maintain normocalcemia (VE + Ca2+) and half were allowed to become hypocalcemic (VE). Filtered load of chloride and total CO2 (TCO2) to the superficial proximal tubule and delivered load to the superficial loop segment were not different between groups. Superficial proximal tubule absolute Cl reabsorption was not different, but superficial loop segment absolute Cl reabsorption was less in the VE + Ca2+ animals (2,221 +/- 106 vs. 2,651 +/- 125 pmol/min, P less than 0.05) and whole-kidney fractional chloride excretion was greater (10.5 +/- 1.6 vs. 4.3 +/- 0.5%, P less than 0.05). When indomethacin (I) was administered to hypocalcemic (VE + I) and normocalcemic (VE + Ca2+ + I) AVE animals, both groups of animals had tubular and whole-kidney chloride reabsorption similar to VE animals. TCO2 reabsorption was not influenced by Ca2+ or I. The data indicate that normocalcemic vs. hypocalcemic AVE results in reduced superficial loop segment chloride reabsorption and greater whole-kidney fractional chloride excretion in the absence but not in the presence of prostaglandin inhibition. The data are compatible with an effect of hypocalcemia during AVE to limit superficial loop segment and whole-kidney chloride excretion by inhibiting renal prostaglandin synthesis.

Hypoxanthine causes a 2-cell block in random-bred mouse embryos.

Ham's F-10, a chemically defined, complex culture medium, commonly used for in vitro fertilization of human as well as animal oocytes, blocked development at the 2-cell stage of greater than 92% of embryos from random-bred Swiss mice (CD-1), but did not block development of embryos from hybrid-inbred mice (BDF1). In contrast, BWW, a simple, modified Kreb's-Ringer bicarbonate medium, supported development to blastocysts of 85% and 100% of 2-cell embryos from CD1 and BDF1 females, respectively. As little as 15% (v/v) Ham's F-10 added to the BWW blocked the development of the random-bred embryos. Supplementing the BWW with Ham's F-10 components revealed that hypoxanthine (6-30 microM) was responsible for the developmental block to the random-bred embryos. The hypoxanthine block was partially (40%) reversed by adding the chelating agent, ethylenediaminetetraacetic acid. Breeding experiments showed that the hypoxanthine sensitivity of embryos from CD-1 mothers was not affected by the paternal genome.

Neonatal Steroid Exposure Increases in Vitro Aromatization Ability of Peripubertal Hamster Ovaries1

Neonatal female hamsters were exposed to doses of testosterone propionate or estradiol benzoate that would lead to behavioral masculinization and defeminization at adulthood. At Days 20, 30, or 40 of life, ovaries were removed and incubated in Kreb's Ringer bicarbonate for 4 h with or without the addition of 1 X 10(-9) M testosterone as a substrate. Incubation medium was assayed by radioimmunoassay (RIA) for the accumulation of estradiol. Ovaries from steroid-exposed animals aromatized testosterone to estradiol at a greatly increased rate compared to ovaries from oil-injected control animals. Serum from treated animals contained androgen, which could act as substrate for aromatization in vivo. Neonatally estrogenized females exhibited elevated circulating estradiol levels. Increased aromatizing ability could be due to early antral follicle formation as a result of elevated luteinizing hormone (LH) and/or follicle-stimulating hormone (FSH). Implications of increased aromatization ability of ovaries in the process of behavioral sexual differentiation are discussed.

Effect of carbachol on rabbit corneal endothelium.

We investigated the current reformulation of the commercially available intraocular preparation of carbachol for its effect on corneal thickness and endothelial cell ultrastructure. A 15-minute perfusion in the specular microscope with 0.01% carbachol caused a significant increase in the corneal swelling rate, which returned to control values after 75 minutes of reperfusion with Krebs Ringer bicarbonate solution. Continued reperfusion with Krebs Ringer bicarbonate solution led to the final average corneal swelling rate being statistically similar to that of controls over the entire 180-minute perfusion period. Transmission and scanning electron microscopy demonstrated no changes in endothelial cell ultrastructure.

In vitro LH release from the hypothalamus-pars tuberalis; effects of gonadotropin-releasing hormone (GnRH), beta-endorphin and biogenic amines.

Immunoreactive and bioactive luteinizing hormone (LH) has been shown to be widely distributed in the rodent central nervous system (CNS), particularly in the hypothalamus. Subcellular localization of this LH in fractions rich in synaptosomes and in vitro release by potassium-induced depolarization suggests that this peptide may act in trans-synaptic neuromodulatory roles. Furthermore, a variety of experiments have proved that this brain-based LH is not of pituitary origin. In the in vitro studies reported here characterization of brain-based LH release, in response to gonadotropin-releasing hormone (GnRH), beta-endorphin, and biogenic amines, was examined. Adult male rats were sacrificed by decapitation, hypothalami removed, quartered, and incubated in Krebs Ringer's Bicarbonate (KRB). High potassium concentration and GnRH induced release of LH from these hypothalamic explants in short-term culture and serotonin significantly inhibited release of LH from these explants. In contrast, however, beta-endorphin, norepinephrine, dopamine, and acetylcholine, agents known to modulate pituitary LH release, had no effect on the release of LH from hypothalamic tissues in vitro. Furthermore, beta-endorphin did not alter potassium-induced release of LH from the hypothalamus. Whereas there are some similarities between LH release from the pituitary and from the CNS, the differences reported here suggest that hypothalamic LH does not simply serve as a supplemental source for LH in the general circulation but more likely subserves an entirely different role(s) than its pituitary counterpart, presumably acting in a neuromodulatory fashion within the brain.

Evidence for dopamine receptor-mediated inhibition of prolactin cell function in the female Syrian hamster.

Since the exact nature of the hypothalamic regulation of prolactin (PRL) cell activity in the photosensitive female Syrian hamster is unknown, the present investigation was designed to determine whether dopamine (DA), a physiological PRL-inhibitory hormone in the rat, inhibits the synthesis and release of female hamster PRL in vitro via a DA receptor-mediated mechanism. Anterior pituitary glands from long photoperiod-exposed adult female Syrian hamsters were incubated in the presence of increasing concentrations of DA (5 nM, 500nM and 50 microM) in Kreb's Ringer Bicarbonate medium for 2 hours following a preincubation period of 1 hour in medium not containing DA. While PRL synthesis, as measured by the incorporation of 3H-leucine into PRL, was unaffected by DA, the release of immunoreactive (RIA)-PRL into the medium was inhibited by 55% and 53% by 500 nM and 50 microM DA, respectively; however, these same concentrations of DA inhibited the release of 3H-PRL into the medium by only 25% and 23%, respectively. The DA receptor blocker, pimozide (PIM) was effective in blocking the PRL-inhibitory effects of DA (500 nM) on both RIA- and 3H-PRL release in vitro. These are the first data suggesting that DA directly inhibits PRL release from female hamster anterior pituitary glands via a DA receptor-mediated mechanism.

Studies on the effect of synthetic amino acid mixtures on bile secretion in the isolated perfused rat liver

Intrahepatic cholestasis may occur in patients receiving parenteral nutrition. Recent work has implicated amino acids in the perfusates in the pathogenesis of this cholestasis. Thus, we examined the effect of currently used amino acid solutions on liver structure and function using the perfused rat liver. Livers from male rats were perfused with Kreb's-Ringer bicarbonate buffer for periods up to 90 min. Two different solutions (Travasol R, Vamin R) were each added to the perfusion medium at amino acid concentrations of 0.05%, to 1.5%. The perfusate was sampled every 15 min for GTP, K + and Na +. Bile flow and bile acid secretion rate were monitored every 15 min. Livers were examined by light and electron microscopy. Infusion of amino acids did not change Na + and K + concentrations in the perfusate but decreased transaminases at all times studied. Bile flow decreased by 20% to 98% in a dose-dependent manner with Vamin R being slightly less cholestatic than Travasol R. Bile acid independent flow (BAIF) of the bile secreted was also reduced. The hepatic ultrastructure following amino acid perfusion was similar to that of livers after buffer alone and indicated absence of cellular damage. This study suggests that the amino acid solutios may induce cholestasis by interfering with the BAIF.

Insulin-like activity of taurine.

There is now an increasing body of data that taurine (2-aminoethanesulfonic acid) at pharmacological concentrations alters carbohydrate metabolism. Early reports from Ackerman and Heinsen (1) and Macallum and Sivertz (10) found that taurine was potent a hypoglycemic agent. Several teams of investigators have confirmed these initial results. Donadio and Fromageot (4) confirmed the hypoglycemic properties of taurine and presented evidence that taurine increased glucose utilization in the rat diaphragm. Lampson et al. (9) reported that taurine was capable of enhancing the effects of insulin on cardiac glycolysis, glycogenesis and oxygen consumption. Moreover, when fasting rats were given a bolus injection of glucose, Kulakowski and Maturo (6) observed that taurine alone was capable of reducing serum glucose levels while stimulating 3-0-methylglucose uptake in skeletal muscle and liver, and glycogenesis in the liver. This occurred without a concomitant increase in serum insulin levels.KeywordsInsulin ReceptorKrebs Ringer Bicarbonate BufferIncrease Glucose UtilizationProline UptakeGlycogen ProductionThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Plasma exchange therapy for endotoxin shock in puppies

The efficacy of plasma exchange (PE) therapy for endotoxin (ET) shock has not been evaluated. The following experimental study was designed to (1) evaluate the feasibility of PE in infants and children and (2) determine the efficacy as a therapeutic modality for ET shock. A compact circuit for PE designed for this experiment consists of two pumps and a membrane plasma separator for a venovenous extracorporeal circulation with the limited prime volume of 100 mL. The capacity of this device for PE was tested. When a membrane separator of 0.3 m 2 in surface area was used, a plasma flux of 5 to 13 mL/min was satisfactorily obtained with the blood flow rate of 25 to 40 mL/min, which was taken through centrally placed catheters of 18 gauge or larger. Transmembrane pressure was maintained in a safe range (0 to 50 mm Hg) in the first 90 minutes, during which time a PE of 100 mL/kg was completed with a sieving coefficient greater than 0.8. In 14 puppies (1.8 to 3.5 kg), a shock state was produced by infusion of ET ( Escherichia coli, 055:B5). Eight puppies were resuscitated simply with lactated Ringer's solution and bicarbonate. Six puppies were treated with PE using 100 mL/kg of fresh-frozen plasma prepared from adult dogs. A significant decrease in the mean blood pressure, platelet and leukocyte counts, total protein, and CH50 was documented in all animals after ET administration. Seven of eight control animals died within 24 hours of post-ET infusion. All of the six PE-treated animals survived for 48 hours or longer. The significant differences between the two groups were found in the mean blood pressure (mean ± SD 72 ± 20 v 103 ± 4 mm Hg), total protein (3.8 ± 0.4 v 5.3 ± 0.4 g/dL), and CH50 (13.0 ± 5.5 v 26.2 ± 6.9 units) measured one hour post-PE. PE is feasible in puppies and may be safely used in infants and children. It is suggested that PE can be a therapeutic modality for ET shock.

Lipoprotein lipase secretion from isolated rat fat cells of different size

Lipoprotein lipase(LPL) release from isolated small fat cells from young rats and large fat cells from older, fatter rats was compared during in vitro incubation at 30°C. Although large fat cells had nearly three times higher cellular LPL activity, they secreted similar amounts of LPL activity into the incubation medium under both basal conditions (Krebs Ringer bicarbonate buffer containing 4% albumin and 6mM glucose) and after stimulation of LPL release by 5% human serum, or serum plus 1 U/ml herapin. These data suggest that previous observations of an altered tissue distribution of LPL in adipose tissue containing large fat cells can be at least in part explained by an alteration at the level of LPL secretion.

BSS Plus: a potential irrigating solution for neurosurgery

BSS Plus is a pH-stable balanced salt solution similar to glutathione bicarbonate Ringer's solution. Extensively used in ophthalmology, it is of potential value in neurosurgery. In comparative tests of its effectiveness, 28 cats underwent bilateral irrigation of the surface of the cerebral cortex with normal saline on one side and BSS Plus on the other. After 2 hours, a marked decrease was seen in the surface pH of the hemisphere irrigated with normal saline but not of the hemisphere treated with BSS Plus. Blood-brain barrier changes (measured with Evans blue dye techniques) were more evident following saline irrigation. Somatosensory evoked potentials and cerebral blood flow were not significantly altered. Conventional light microscopy using three standard stains did not reveal a significant difference. Transmission electron microscopy studies were performed in 14 animals and scanning electron microscopy in six. In five animals both transmission and scanning electron microscopy studies were conducted after irrigation with both agents without a cottonoid cover and with immediate harvest of superficial layers from the living brain and immersion-fixation in glutaraldehyde. Tissue preservation was superior on the BSS Plus side in all studies. This agent may represent an improved irrigation solution for neurosurgery, but further studies are required.

Synthesis of stress-induced protein in isolated and perfused rat hearts.

Isolated and perfused rat hearts were examined by two-dimensional gel electrophoresis and liquid scintillation counting for alterations in protein synthesis following incubation with L-[3H]leucine at 0.5-2.5, 2.5-4.5, or 4.5-6.5 h of perfusion. When 35-mL volumes of three different buffers were recycled for a 2-h period from 0.5 to 2.5 h, by fluorography little effect was seen on the normal patterns of protein synthesis and there was a moderate synthesis of a stress-induced protein (heat-shock protein) with a molecular mass of 71 X 10(3) daltons (SP71). However, hearts perfused with Krebs-improved Ringer 1 bicarbonate had the highest incorporation of L-[3H]leucine. When buffers were recycled for 30-min periods from 0.5 to 2.5 h, SP71 was synthesized in hearts perfused with Krebs-Henseleit original Ringer bicarbonate. Hearts perfused in a similar fashion with Krebs-improved Ringer 1 bicarbonate had the lowest incorporation of label into SP71 and in fact SP71 was undetectable on fluorograms. Overall protein synthesis was decreased and the ratio of SP71 to the total synthesis was increased at 4.5-6.5 h of perfusion when 35-mL volumes of Krebs-improved Ringer 1 bicarbonate was recycled for 2-h periods. A similar result was observed at 2.5-4.5 h of perfusion when this buffer was recycled for either the duration of the experiment or 30-min periods.

Myo-Inositol metabolism and (Na+ + K+)-ATPase activity in relation to peripheral nerve function in rats with streptozotocin-induced diabetes

Experimental diabetes in the rat is associated with a well-characterized decrease in motor nerve conduction velocity (Gillon et al., 1983). In rat sciatic nerve, induction of diabetes results in marked elevation of the concentrations of glucose, sorbitol and fructose, whereas the concentration of myo-inositol is reduced (Palmano et al., 1977). Diabetic nerve malfunction may occur as a result of a relationship between the increased polyol pathway activity, the decreased free myo-inositol concentration and an alteration in the activity of the enzyme (Na' + K+)ATPase. The present study was designed to examine the possibility of such a correlation and to investigate a report by Greene & Lattimer (1983) that (Na+ + K+)ATPase activity is lower in sciatic nerve homogenates from diabetic rats compared with that in homogenates from control rats. The steady-state rate of energy utilization is known to be decreased in diabetic nerves (Greene & Winegrad, 1981). This study compares the rates of ouabain-sensitive 86 Rb+ uptake by endoneurial preparations from diabetic and control rats. Diabetes was induced in male Wistar rats (253-314 g) by a single intraperitoneal injection of streptozotocin (60 mg/kg body wt.) in 0.2 ml of 50 mM-sodium citrate buffer. Age- and weight-matched controls received a similar volume of buffer alone. Animals whose blood glucose concentration exceeded 16 mM 2 days after injection were included as diabetics in the study. Diabetic and control animals were divided into two groups and used at either 4 or 6 weeks after injection. Sciatic nerves were removed from the rats under pentobarbitone anaesthesia (60 mg/kg body wt., by intraperitoneal injection). Two ligatures (with 5/0 grade silk) were applied to each nerve before excision, one at the sciatic notch and the other approx. 4cm distal to the first. The epineurium and the perineurial membrane were removed from the ligated nerves by the method of Gillon & Hawthorne (1 983) and two more ligatures were applied at the centre of the resulting endoneurial preparation. The nerve was bisected between these ligatures to yield two endoneurial preparations from each sciatic nerve. Endoneurial preparations were incubated at 37°C for 20 min in Krebs-Henseleit bicarbonate Ringer solution (Krebs & Henseleit, 1932) containing 4% (w/v) bovine serum ium ion-dependent adenosine triphosphatase. Abbreviations used: (Na+ + K+ )-ATPase, sodium ion-plus-potass

PH sensitivity of the basolateral membrane of the rabbit proximal tubule

Conventional microelectrodes were used to study the effects of bath pH and bicarbonate concentrations on the basolateral membrane potential (Vbl) of cells from the superficial proximal convoluted (PCT) and proximal straight (PST) tubules of the rabbit kidney perfused in vitro. Bathing solution pH was varied over the range of 5.9-7.4 using either control (22-25 mM) or low bicarbonate (5.0-6.6 mM) Ringer solutions and the appropriate CO2 tensions. The results show a strong pH dependence of the steady-state values of Vbl in both the convoluted and straight tubule segments. The pH-dependent depolarization was approximately 35 mV/pH unit change of the bathing solution in the acid direction and could be demonstrated in CO2-free HEPES-buffered solutions. A depolarizing response to increased bath potassium concentration (HK) was observed that was linearly related to the absolute value of the Vbl under control conditions. Under acidotic conditions, reduced HK depolarizations indicate that a decrease in the relative potassium permeability of the basolateral membrane is the principle mechanism underlying the effects of bath pH on Vbl.

Steroid sequestration and tightly bound oestrogen-protein complexes in human breast tumours and a breast cancer cell line

Homogenates of breast tumours taken at surgery were prepared in phosphate-buffered medium in the presence or absence of the protease inhibitors N- α- p-tosyl- l-arginine methyl ester (TAME, 10 mM) or soy bean trypsin inhibitor (STI, 1 mg/ml). Aliquots (0.25 ml) were incubated in 5 ml medium, with the addition of excess trypsin (2 mg/ml) to experimental flasks. Oestrogen was measured by means of a radioreceptor assay (RRA) based on rat or human uterine cytosolic oestradiol receptor. In oestrogen receptor positive (ER +ve) tumour homogenates, TAME decreased while STI increased ethyl acetate extractable oestrogen in these preparations. The addition of trypsin enhanced yields of oestrogen in the TAME, but not in the STI or control (no inhibitor) preparations. None of these treatments affected RRA detectable oestrogen in homogenates of ER −ve tumours. Suspensions of ZR-75-1 cells, prepared in Krebs Ringer bicarbonate (KRBG) incubated with trypsin also gave greatly enhanced yields of extractable oestrogen. Fractionation of oestrogens from both tumour homogenates and from the cell line showed coincidence of RRA detectable steroid with oestradiol and oestrone, and, particularly in trypsin flasks, very non-polar components were also found. In the cell-line extracts, HPLC fractionation combined with specific radioimmunoassays confirmed the presence of both oestradiol and oestrone. The major extracted component was oestrone. The data suggest the existence within breast tumour tissue of sequestered pools of steroid requiring proteolytic action for their release. One possibility, consistent with reports in the literature, is that the steroids may themselves be directly conjugated to protein. Their presence in ER +ve but not ER −ve tumours strongly suggests some relationship to the development of hormone-sensitive disease. Alternatively, the phenomenon may be associated with the rigid compartmentalization of the paracrine function of the tissue.

Release of prostaglandins E and F from rat uterine strips incubated in depolarizing and hyperpolarizing solutions

The purpose of this study was investigate the effect of depolarizing (high K +, procaine 5mM, high K +Ca 2+ free) or hyperpolarizing (K + free)solutions on the generation and release of prostaglandins (PGs) E and F from the rat uterus. The output of PGs in the bathing solution was measured by bioassay. Results are expressed as ng/g dry weight/min. Under basal conditions in Krebs Ringer Bicarbonate medium, the total output of PGs (E + F) was 12.8 ± 0.9, 20.5 ± 2.5 and 39.1 ± 4.3 ng/dw/ min at 0–60, 60–80, 80–100 min intervals respectively, the major proportion being PGF like material in all cases. When the strips were bathed in depolarizing solution the total output increased significantly PGE being the most augmented. However, when K + free solution was used there was a marked reduction in prostaglandins release as compared with basal conditions or depolarizing media. These results can not be attributed to osmotic effect, muscular work or neurotransmitter release from nerve endings. A close relationship between the variations in membrane potential and prostaglandins release seems to indicate that both parameters might correlate well.

PH lability in serum during equilibrium dialysis.

Changes in pH were determined in previously frozen normal human serum during dialysis against sodium phosphate, Krebs Ringer phosphate or Krebs Ringer bicarbonate buffers of pH 7.4. Serum was either untreated (native) or adjusted to pH 7.4 before dialysis. pH in native serum was 7.7-7.9 before dialysis, showed a decrease after 1 h, and an increase after 3 h. pH-adjusted serum showed a continuous pH increase during dialysis. The increase in serum pH during dialysis was larger at 37 degrees C than at 22 degrees C, larger at low than at high buffer molarity, and larger in native than in pH-adjusted serum. The observed changes in serum pH during dialysis are associated with unacceptably large errors in unbound fraction in serum for a number of important drugs. Drug binding determination in serum by equilibrium dialysis should be performed with buffers providing appropriate and stable pH level.

Effects of adenosine on renin release from isolated rat glomeruli and kidney slices.

Adenosine produced by the macula densa cells in response to changes in the tubular NaCl-concentration has been suggested to inhibit renin release in vivo. In order to test this suggestion we studied: incubated kidney cortical slices (KS) which contain both the macula densa and the entire afferent arteriole; superfused single microdissected glomeruli (LAG) without macula densa but with the afferent arteriole preserved; and superfused batches of selected glomeruli (SAG) containing only the juxtaglomerular cells closest to the glomerulus. For superfusion and incubation a bicarbonate Ringer solution was used. The specificity of the renin release process was validated by measuring adenylate kinase as a marker for cytoplasmatic leak. Adenosine (10 micrograms/ml) halved basal renin release from incubated KS as compared to controls (P less than 0.001, n = 8, 8). Renin release from LAG stimulated by calcium depletion was also inhibited (P less than 0.05, n = 8, 9) whereas basal release was not affected (n = 6, 12). No effect was detected neither on basal nor on calcium stimulated renin release from SAG. We conclude that adenosine inhibits renin release in vitro by a mechanism independent of a functioning nephron, and which involves only the JG-cells located in the afferent arteriole at some distance from the glomerulus.

Modes of endocytosis of latex particles in sinusoidal endothelial and kupffer cells of normal and perfused rat liver

The endocytosis of latex particles (0.33, 0.46 and 0.80 μm in diameter) in the sinusoidal endothelial and Kupffer cells of the rat liver was studied electron microscopically. When the liver was perfused with serum-free oxygenated Krebs Ringer bicarbonate, latex particles of all three sizes were taken up by the endothelial cells. After a 10-min perfusion, particles were incorporated by the luminal cell surface of the perikarya or of the thick portion of the endothelial cells. A large patch of bristle coat was surrounding the ingested particle. The number of ingested particles in the endothelial cells, however, was much less than in the Kupffer cells. In in vivo experiments, no endocytosis of the latex particles was observed in the endothelial cells. In the Kupffer cells, particles were engulfed by the ruffled membranes or sank into the cytoplasm without a large patch of the bristle coat both in the perfusion system and in vivo. These observations show that at least 0.80 μm latex particles are taken up by the bristle-coated membranes in the sinusoidal endothelial cells of the perfused liver. The endocytic mechanism for latex particles in the endothelial cells is different from that of the Kupffer cells.

Vascular perfusion: a novel means of studying oviduct function

An in situ preparation for the combined vascular and luminal perfusion of the rabbit oviduct has been developed. Medium 199, gassed with 5% CO2 in O2 and supplemented with heparin, antibiotics, and 2.5% wt/vol dialyzed bovine serum albumin was infused into the ovarian artery at a rate of 1 ml/min. Krebs Ringer bicarbonate medium was recirculated through the lumen at a rate of 50 microliter/min. The ovary was perfused together with the oviduct, and the preparation is viable for up to 3 h. Equal concentrations of pyruvate, lactate, glucose, and sucrose added to the vascular medium were transported at different rates into the lumen, as was a physiological mixture of amino acids. A proportion of the lactate entering the lumen was synthesized within the oviduct from vascular glucose. When glucose and pyruvate were omitted from the vascular medium, their appearance and that of lactate in the lumen was barely detectable, suggesting that these oviduct fluid components are mainly derived from the blood. The oviduct maintained a steady transmural potential difference of 5.9 mV (lumen negative). With vascular perfusion alone, oviduct fluid entered the oviduct lumen at a rate of 16.8 microliter/h. In oviducts taken from rabbits 3 days postovulation, there was a general decrease in the vascular to lumen flux of all nutrients measured. Preliminary work has shown that the preparation may be used to study ovulation, ovum pickup and transport, and fertilization.