Ultrastructural observations of the adenohypophyseal gonadotrophs from growth selected lines of chickens

The ultrastructure of adenohypophyseal gonadotrophs (GT-cells) from pullets of lines selected for high (HWS) and low (LWS) body weight was studied at various physiological ages. Increasing the photoperiod beyond 14 hours in a 24-hour cycle did not have a significant effect on the ultrastructure of GT-cells in either line. A qualitative analysis, based on the extent and complexity of the protein synthetic apparatus, suggested that the synthetic activity of gonadotrophs from HWS pullets was greater than that of LWS pullets at each of the ages studied. Although no significant differences were found in the frequency of pullets showing evidence of intracellular digestion of secretory products, the condition was more severe in the HWS than in the LWS females. Crinophagy tended to be positively correlated with cell activity in both lines. These observations suggest that selection for growth rate had a correlated effect on hypophyseal proteinaceous secretions. They also indicate that interactions between fluctuations in gonadotrophic cell activity, secreting mechanisms and neural thresholds for hormone action may be implicated in the manifestation of the erratic ovulation patterns.