Growth Hormone Receptors in Testis and Liver: RESULTS(2)

25 Nov

The specificity of GH binding sites to crude testicular preparation was tested in competition experiments (Fig. 2). Unlabeled rtGH at concentrations of 0.1-250 ng/tube inhibited the specific binding of the tracer. Bovine GH and rtiGH competed with 125I-rtGH in a dose-dependent manner but appeared to be 75- and 350-fold less effective (calculated at 50% displacement), respectively, than unlabeled rtGH. Bovine insulin, sPRL, oPRL, tGtHl, and tGtH2 did not significantly compete with 125I-rtGH from the binding sites at the tested concentrations. asthma inhalers

Evolution of GSI and HSI during Spermatogenesis

In autumnal (fall spawning) rainbow trout, after 1 or 2 yr of prepubertal immaturity (stage I), spermatogenesis developed more or less synchronously in the whole gonad from March-April (stage II, only spermatogonia) to N0vember-December (stage VIII, spermatozoa). The GSI increased rapidly during this period (Fig. 3a), whereas the HSI varied from 1% to 1.3% and appeared significantly higher in the first stages (II-IV) than in stages V-VIII of spermatogenesis (Fig. 3b).
Fig2Growth hormone receptors
FIG. 2. Competition curves for specific binding of [l25l]rtGH (30 000 cpm/tube) to crude testicular preparation (50 mg of pellet per tube, stage V) with increasing amounts of unlabeled hormone preparations. Binding is expressed as a percentage of [,25l]rtGH specifically bound in absence of competitor.

Fig3Growth hormone receptors
FIG. 3. Evolution of a) GSI and b) HSI in rainbow trout during spermatogenesis. Number of fish analyzed is shown in parentheses above histograms. “””Indicates significant differences (p < 0.01). Results are expressed as the mean + SEM.