Day-night differences in membrane-bound pyroglutamyl-2-naphthylamide-hydrolyzing activity in rat hypothalamus, pituitary, and retina.

Membrane-bound pyroglutamyl-2-naphthylamide-hydrolyzing enzyme activity was analyzed fluorometrically in the anterior hypothalamus, pituitary, and retina of adult male rats to investigate day-night differences. Six groups (n=6 per group) were assessed--three during the light span and three during the dark span--under a standard 12 h-12 h light-dark cycle (light on from 07:00 to 19:00 h) and controlled temperature environment, with food and water available ad libitum. In the hypothalamus, enzyme activity levels were higher for time points of the dark than the light period. In contrast, the pituitary and retina exhibited the highest levels at the time points of the light period. The pituitary and retina also exhibited significant differences between the clock-hour means of the light period. Day-night differences in membrane-bound pyroglutamyl-2-naphthylamide-hydrolyzing activity may reflect differences in its susceptible endogenous substrates.

Aminopeptidases in the gonads of male and female rats.

OBJECTIVE: To assess the relative importance of soluble (Sol) and membrane-bound (M-B) components of aminopeptidase (AP) activities in local functions of male and female gonads. DESIGN: Observational study. SETTING: University research. ANIMAL(S): Adult male and female Sprague-Dawley rats in the proestrous phase of the estrous cycle. INTERVENTION(S): Samples from the right testis and the whole right ovary were dissected after perfusion with saline. The Sol and M-B fractions were obtained from these samples. MAIN OUTCOME MEASURE(S): Fluorometric measurement of Sol and M-B AP activities using arylamide derivatives as substrates. RESULT(S): Highly significant differences between male and female gonads were observed. Sol AP activities showed a significant predominance in testes, whereas M-B AP activities were significantly higher in ovaries. CONCLUSION(S): There was a discrepancy in the distribution of Sol and M-B AP activities between male and female gonads, which may imply a direct participation of sex steroids in AP activities. These results may reflect the relative importance of these enzymes in the testis and ovary and should be taken into account in evaluating the functional role of peptides locally produced in gonads.

Dietary fatty acid composition affects aminopeptidase activities in the testes of mice.

The autocrine/paracrine control mechanisms of local factors, such as the renin-angiotensin system and the thyrotropin-releasing hormone (TRH), seem to play a relevant role in testicular physiology. It has been proposed that dietary fat composition influences male reproductive function modifying the cholesterol-phospholipid composition of testicular plasma membranes. Modifications in the composition and physical properties of the membranes may lead to alterations in the activities of membrane-bound (M-B) enzymes. We have previously demonstrated that cholesterol and steroid hormones affect aminopeptidase (AP) activities. Dietary fatty acids with different degrees of saturation modified AP activities in the serum of mice and an olive oil supplemented diet influenced the AP activities in the testes of mice. We hypothesized that the modification of dietary fat composition may affect angiotensin- [glutamyl-AP (GluAP), aspartyl-AP (AspAP)] and TRH- [pyroglutamyl-AP (pGluAP)] degrading activities in the testis. In this study, we investigated the effect of diets supplemented with sunflower oil (SFO), fish oil (FO), olive oil (OO), lard (L) or coconut oil (CO) on soluble (Sol) and M-B GluAP, AspAP and pGluAP in mice testis, using arylamides as substrates. Sol GluAP activity did not show differences among groups. However, Sol AspAP and Sol pGluAP progressively decreased with the degree of saturation of the fatty acid used in the diet. In contrast, M-B GluAP progressively increased with the degree of saturation of the fatty acid used in the diet. For M-B AspAP activity, mice fed diets containing FO showed significantly higher levels than those fed diets containing SFO, OO and L but not those containing CO. For M-B pGluAP activity, the highest levels were observed for mice fed diets containing FO and OO. The present data suggest that the type of fat used in the diet may influence the autocrine/paracrine functions of locally synthesized angiotensin peptides and TRH in the testis, and consequently may be important in male reproductive functions.