Involvement of MAP kinase in the mediation of GH action on ovarian granulosa cells.
Growth hormone (GH), prostaglandins F (PGF) and prostaglandins E (PGE) are important regulators of ovarian function. Therefore, interrelationships between GH and these substances and their intracellular mechanisms might be of physiological significance in the ovary. The aims of this study on cultured porcine ovarian granulosa cells were to determine the effect of GH on the secretion of oxytocin (OT), PGF and PGE and whether MAP kinase could be involved in the mediation of GH action. Experiments were carried out with cultured porcine granulosa cells to investigate the effects of exogenous pGH (1-100 ng/ml) on the expression of MAP kinase (ERK-1, -2) and of PGH (1-100 ng/ml) and the MAP kinase blocker PD 98059 (1 microg/ml) on the secretion of PGF, PGE and OT. The cellular content of ERK-1 and -2 was analyzed by Western immunoblotting and immunocytochemistry, whilst PGF, PGE and OT accumulation in the medium was measured by RIA. Addition of GH to culture medium significantly altered the pattern of ovarian ERK MAP kinase on SDS-PA gels: the 44 and 42 kDa bands were reduced and additional 50 and 48 kDa bands appeared. Moreover, there was an increase in the percentage of cells containing ERK MAP kinase. GH stimulated the secretion of PGF (at a concentration of 1 ng GH per ml medium) and OT (100 ng GH per ml), but not PGE. The MAP kinase blocker alone did not affect PGF, PGE and OT secretion but did prevent the stimulatory effects of GH on PGF and induced stimulatory action of GH (10 ng/ml) on PGE. GH-stimulated OT secretion was unaffected. These observations confirm the role of GH in regulating porcine ovarian PGF, PGE and OT secretion and the presence of ERK MAP kinase in porcine granulosa cells. Furthermore, our studies demonstrate that MAP kinase-dependent intracellular mechanisms are dependent on GH, and that these mechanisms are involved in the mediation of GH action on ovarian PGF and PGE but not OT secretion.
Sirotkin
Alexander V
AV
Endocrinology Laboratory, Research Institute of Animal Production, Hlohovská 2, 949 92 Nitra, Slovakia. sirotkin@vuzv.sk
Makarevich
A V
AV
Kwon
H B
HB
Kotwica
J
J
D000818:Animals; D002478:Cells, Cultured; D005260:Female; D006107:Granulosa Cells / Q000187:drug effects / Q000201:enzymology* / Q000502:physiology; D013006:Growth Hormone / Q000494:pharmacology*; D020930:MAP Kinase Kinase Kinases / Q000037:antagonists & inhibitors; D020935:MAP Kinase Signaling System; D020928:Mitogen-Activated Protein Kinases / Q000502:physiology*; D010121:Oxytocin / Q000096:biosynthesis; D011453:Prostaglandins / Q000096:biosynthesis; D013552:Swine
D011453:Prostaglandins; D010121:Oxytocin; D013006:Growth Hormone; D020928:Mitogen-Activated Protein Kinases; D020930:MAP Kinase Kinase Kinases