Antenatal glucocorticoids modulate the amplitude of pulsatile cortisol secretion in premature neonates.

We hypothesized that antenatal exposure to glucocorticoids influences subsequent pulsatile cortisol (F) secretion in premature neonates. To test this hypothesis, blood was sampled for plasma F determination via indwelling arterial lines at 15-min intervals for 6 h in 26 clinically stable neonates whose gestational ages were 25-33 wk. Deconvolution analysis was used to characterize F secretion and elimination. Pulsatile F secretion was observed in all neonates. Deconvolution estimates in eight neonates exposed to antenatal glucocorticoids (ANG group) were compared with those of 18 neonates not or only remotely exposed to ANG (No/RG group). The median amplitude of the F secretory burst of the ANG group was significantly less than that of the No/RG group [4.3 nmol/Lv x min and 9.2 nmol/Lv x min, respectively; p = 0.026 (Lv is liter of F distribution volume)]. The number and duration of F secretory bursts was similar for both groups: 5 bursts per 6 h, and 23 versus 16 min. By univariate linear regression analysis, mean arterial blood pressure correlated positively with F secretory burst frequency and F production rate (p = 0.0035, r = 0.55 and p = 0.0067, r = 0.52, respectively). We propose that ANG treatment modulates the amplitude of pulsatile F secretion in premature neonates.

Endogenous energy production by mature boar spermatozoa.

When incubated in the absence of exogenous substrates, washed boar spermatozoa maintained a high energy charge potential (ECP) for at least 5 h. Addition of 3-chloro-1-hydroxypropanone, an inhibitor of triosephosphate isomerase and glyceraldehyde 3-phosphate dehydrogenase, at any time caused the ECP to decline and fructose-1,6-bisphosphate, dihydroxyacetone phosphate and glycerol to accumulate. There appear to be two endogenous substrates that are degraded ultimately to produce the triosephosphates which allow the cells to produce lactate for the mitochondrial synthesis of ATP. One substrate generates minor amounts of glycerol 3-phosphate whereas the other substrate degrades to glycerol and may be di-glycerides, or tri-glycerides, or both.

The anti-glycolytic activity of 3-bromopyruvate on mature boar spermatozoa in vitro.

Mature epididymal boar spermatozoa converted fructose, glycerol and glycerol-3-phosphate to carbon dioxide, but in the presence of 0.5 mM 3-bromopyruvate, these oxidations were inhibited while that of lactate was unaffected. Inhibition of the oxidation of these substrates results in a decrease in the content of ATP and the accumulation of dihydroxyacetone phosphate and fructose-1,6-bisphosphate. Examination of the activities of the enzymes within stage two of the glycolytic pathway showed that glyceraldehyde-3-phosphate dehydrogenase and 3-phosphoglycerate kinase were immediately inhibited by 3-bromopyruvate in a competitive manner. We now report the action of 3-bromopyruvate on the metabolic activity of boar spermatozoa. At a concentration of 0.5 mM, this compound selectively inhibits stage two of the glycolytic pathway and becomes yet another specific inhibitor of spermatozoal metabolism.