Compartmentation of 14CO2 in the perfused rat liver

The specific activity of the mitochondrial CO2 + bicarbonate system has been measured in perfused livers using the specific activities of urea and acetoacetate derived from 2-ketoisocaproate catabolism. Label was supplied either as NaH14CO3, 2-keto[1-14C]isocaproate, [1-14C]pyruvate, [1-14C]glutamine, or [14C]formate. With labeled bicarbonate, pyruvate, or 2-ketoisocaproate, the specific activities of effluent bicarbonate, urea, and acetoacetate were equal (acetoacetate was labeled only on C-1). In the presence of [14C]formate, the specific activity of acetoacetate was double that of urea. Acetazolamide (0.2 mM), an inhibitor of carbonic anhydrase, decreased the specific activities of urea and acetoacetate labeled from NaH14CO3 and increased the specific activities of urea and acetoacetate labeled from the other tracers. We conclude that: acetoacetate derived from 2-ketoisocaproate is, like urea, an index of the specific activity of mitochondrial CO2 in liver, carbonic anhydrase activity equalizes the specific activities of the CO2 + bicarbonate system on both sides of the mitochondrial membrane, and a fraction of [14C] formate-derived 14CO2 appears to be generated in a mitochondrial compartment, in the close vicinity of methylcrotonyl-CoA carboxylase.

Renal prostaglandins E2 and F2 alpha throughout normal human pregnancy

Twenty-five normal pregnant women were studied sequentially at 4-week intervals, beginning from weeks 8-16 until delivery. In eighteen women the study was repeated 6 weeks after delivery. The 24-h urinary excretion of PGE2 and PGF2 alpha, plasma renin activity (PRA), plasma aldosterone and fractional excretion of sodium (FENa) were measured at each visit. PGE2 and PGF2 alpha increased progressively throughout pregnancy (867 +/- 81 and 1048 +/- 94 ng 24 h-1 respectively, before week 15 and 1581 +/- 175 and 2625 +/- 305 ng 24 h-1, respectively, after week 35) and returned to normal values 6 weeks after delivery (748 +/- 107 and 1503 +/- 165 ng 24 h-1, respectively). PRA and aldosterone increased in a similar fashion, but values of prostaglandins did not correlate with those of PRA or aldosterone. PGE2 correlated directly with FENa but this correlation was weak. These results may suggest that tubulo-interstitial prostaglandins play a role in the regulation of sodium homeostasis during pregnancy.

Determination of the concentration and specific activity of acetone in biological fluids

The concentration of acetone dissolved in liver perfusion medium was determined by injection of the sample into a gas chromatograph equipped with a Carbopack/Carbowax-packed glass column. Interference from labile acetoacetate which readily decomposes to acetone was eliminated by treating the samples with NaBH4 prior to the analysis. Acetone was detected and quantified as 2-propanol. Separation of labeled 2-propanol in the sample by high-performance liquid chromatography allowed the determination of its specific activity. These methods make possible the convenient and rapid determination of acetone concentration and specific activity in biological samples.

Characterization of monoclonal antibodies against prostaglandin E2: fine specificity and neutralization of biological effects

The specificity and heterogeneity of the immune response of BALB/c mice immunized with prostaglandin E2 (PGE2) coupled to thyroglobulin was studied. All the animals (n = 50) responded to PGB2, a transformation product of PGE2. However, following repeated injections most of the animals (n = 30) were also able to respond to PGE2. Cellular hybridizations were performed and five anti-PGE2 monoclonal antibodies were isolated and analysed. They are mainly directed against the ring and the omega-chain of PGE2 but their specificity toward the alpha-chain is more limited. The association constants are greater than to 1 X 10(9) M-1. The monoclonal antibody 8E.57.71 (Ka = 1.3 X 10(10) M-1) is particularly convenient for sensitive radioimmunoassays (detection limit 25pg/ml, when iodinated tracer is used). Anti-PGE2 monoclonal antibodies were found to neutralize the specific binding of [3H]PGE2 to rat brain hypothalamic receptors and to inhibit the PGE2 induction of rat fundus muscular contraction.

Humoral growth factor after small intestinal resection in the dog

The serum of dogs with a 50% proximal small bowel resection is capable of growth stimulation in small intestinal epithelioid cells in monolayer culture. This overstimulation by postresection serum is not seen when dogs undergo either a small intestinal transection or a simple laparotomy or with baby hamster kidney fibroblast cells in culture. The effect does not seem to be represented by a gastrinlike molecule. This study lends support to the hypothesis that a humoral factor is involved in small intestinal adaptation after partial resection.