GLUCOSE AND FREE FATTY-ACID MODULATION OF GROWTH-HORMONE AND LUTEINIZING-HORMONE SECRETION BY CULTURED PORCINE PITUITARY-CELLS

The influence of glucose and free fatty acids (FFA) on LH and GH secre tion from porcine pituitary cells was examined in culture. Cells were challenged with 10(-9), 10(-8), or 10(-7) M GnRH; 10(-9), 10(-8), or 1 0(-7) M [Ala(15)]-h growth hormone-releasing factor-(1-29)NH2 (GRF); 1 0(-3) or 10(-5) M forskolin; glucose (100, 300, or 600 mg/dL); and ole ic or linoleic acid (10(-11) to 10(-5) M) individually or in combinati ons of glucose, oleic, and linoleic acid with GnRH, GRF, or forskolin. Relative to control (medium alone), GnRH increased(P < .003) LH secre tion. Glucose at 100 mg/dL enhanced (P < .05) basal LH release, wherea s the 600-mg/dL dose suppressed(P < .05) LH response to GnRH. Except f or 10(-7) M, all doses of linoleic acid increased (P < .05) basal LH r elease, whereas only 10(-5) M linoleic acid suppressed(P < .02) LH res ponse to GnRH. All doses of oleic acid enhanced (P < .05) basal LH rel ease and suppressed (P < .03) the LH response to GnRH. In contrast, ne ither FFA suppressed the forskolin-induced LH secretion compared to fo rskolin alone. Growth hormone-releasing factor stimulated (P < .02) GH release in a dose-dependent manner. Glucose did not alter basal GH re lease but suppressed (P < .01) GRF-induced GH release. Only 300 mg/dL of glucose suppressed (P < .05) forskolin-induced GH release. Only 10( -9) M linoleic acid suppressed (P < .04) basal GH secretion, whereas 1 0(-11) and 10(-9) M oleic acid suppressed and 10(-7) and 10(-5) M olei c acid enhanced (P < .04) GH release. However, both FFA suppressed (P < .03) GRF-induced GH release. Neither FFA affected forskolin-stimulat ed GH secretion. These results indicate that FFA and glucose may direc tly modulate LH and GH secretion at the level of the pituitary gland.