CELL-PHYSIOLOGICAL STUDY ON THE INHIBITORY ACTIONS OF VOLATILE FATTY ACIDS ON THE GH RELEASE FORM RUMINANT SOMATOTROPES

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We obtained the following results with caprine and ovine anterior pituitary cells :1)A rise in GH release from ovine and caprine anterior pituitary cells in response to GRF or GHRP stimulation was significantly inhibited by an addition of VFA in the medium (acetate, propionate and butyrate : 10 mM), where the cells were perifused immediately after cell dispersion or were cultured for 3 days and incubated in the culture dishes.2)The antagonist for L-type calcium channels (nifedipine) completely inhibited, while the antagonist for the non-specific cation channels (tetramethrine) never affected, the GH release induced by GRF stimulation.3)We got the following results using the whole-cell patch clamp method : A.Application of depolarization pulse to the cultured cells caused an increase in inward current at the holding potential was set at - 20 mV.B.The inward current was completely abolished by an addition of nifedipine or fatty acids in the bath medium. Form these results we conclude that volatile fatty acids inhibit the GH release induced by GRF or GHRP stimulation, which is probably due to the inhibitory effects of volatile fatty acids on calcium channels on ruminant somatotropes.