Cellular basis for gender-dependent differences in growth hormone secretion in young chickens: analysis using reverse hemolytic plaque assays.

In young broiler chickens, males exhibit a greater body weight than females. This gender difference in body weight coincides with higher serum growth hormone (GH) concentrations in young males than in juvenile females. The cellular basis for this gender-dependent difference in GH secretion was addressed in the present study. Anterior pituitary cells from 4- to 5-week-old male and female broiler chickens were subjected to reverse hemolytic plaque assays for GH. The percentage of cells that formed GH plaques and average areas of plaques formed were compared between the genders. Maximal plaque formation was found to occur by 4 h of incubation regardless of sex or treatment. Data analysis identified a significant (p < 0.05) gender by treatment interaction. In the presence of GHRH, there was an increased percentage in plaque formation in males (p < 0.05), but GHRH did not affect the percentage of GH secreting cells in cultures from females (p = 0.26). Males were found to have a higher (p < 0.05; n = 6) percentage of somatotrophs than females (e.g. 20.8 +/- 1.2% vs. 13.2 +/- 2.6% of all cells, respectively, after 4 h of detection in the presence of GHRH). Moreover, high levels of GH-Releasing Hormone induced formation of 1.5-fold larger (p < 0.01) plaques around somatotrophs derived from males than those derived from females. The data presented here suggest that gender-dependent differences in GH secretion in young broiler chickens result from differences in the percentage of pituitary cells that release GH, the relative secretory capacity of each individual somatotroph and the responsiveness of the somatotroph populations to GHRH.