CA2-DEPENDENT PROTEIN-KINASE-C ISOFORMS IN RAT PITUITARY HYPERPLASIA - EFFECT OF IN-VIVO TREATMENT WITH QUINAGOLIDE()

Ca2(+)-dependent protein kinase C (PKC) activity, diacylglycerol level s and PKC alpha, beta(I), beta(II), and gamma expression were analyzed in the pituitary of female rats treated with estradiol alone (2 month s) or in combination with quinagolide in the second month. Polymerase chain reaction (PCR) and Western blot analysis revealed the presence o f PKC alpha, beta(I) and beta(II) isoenzymes in the rat pituitary glan d but not of PKC gamma isoenzymes. Increases in pituitary weight and p lasma prolactin levels induced by estradiol were associated with an in crease in diacylglycerol pituitary content (1.55 +/- 0.06 versus 1.12 +/- 0.17 nmol diacylglycerol/mg protein in controls, P < 0.01). Cotrea tment with quinagolide reversed these effects. Changes in PKC activity were accompanied by parallel changes in PKC alpha and beta(I) express ions. Estradiol treatment increased the expression of these isoforms w hereas cotreatment with quinagolide antagonized these effects. PKC bet a(II) expression was not affected. In conclusion, Ca2+-dependent PKC a ctivity and protein expression are increased in hyperplastic pituitary cells, suggesting the involvement of this class of PKCs in the rat pi tuitary cell proliferation and/or hormonal secretion. This is further assessed by the fact that the dopamine receptor agonist treatment decr eases activity and expression of these PKCs in parallel with the decre ase in hormonal secretion and cell proliferation.