TRANSLOCATION OF PROTEIN-KINASE-C ISOZYMES IN RAT PITUITARY LACTOTROPH-ENRICHED CELL-CULTURES BY SUBSTANCE-P - EFFECTS OF SEX AND AGE

It is generally accepted that the phospholipid and calcium-dependent e nzyme protein kinase C (PKC) plays a significant role in secretion of hormones from anterior pituitary cells. The present study was undertak en to study age and sex-related changes in 1, levels of immunoreactivi ty of PKC isozymes and,distribution of immunoreactivity of PKC isozyme s after stimulation with substance beta (SP) in rat lactotroph-enriche d cell cultures. The alpha, beta, delta and zeta isozymes were present in both sexes and at all ages. There was a sex-specific differential regulation of the different PKC isozymes as a function of sexual matur ation. In male rats there was an up-regulation of the alpha isozyme th roughout the sexual development, while the beta subtype showed a small , but significant decrease in immunoreactivity with increasing age. In female rats, on the other hand, the beta species was up-regulated wit h increasing age while the other subtypes remained constant. The conce ntration of the delta and zeta isozymes was unaffected of sex and age. Stimulation of lactotroph-enriched cell cultures with substance P (SP ) resulted in translocation of the alpha and beta isozymes from the so luble to the particulate fraction while the delta and zeta species wer e left unchanged independently of age and sex. However, a decrease in responsiveness was observed in adult male rats, although a significant degree of translocation of alpha and beta species was still detected. On the basis of these results it is suggested that in lactotroph-enri ched cell cultures basal levels of PKC subtype immunoreactivity and di stribution of immunoreactivity of PKC isozymes after SP challenge migh t be regulated as a function of sex and age.