DIFFERENTIAL-EFFECTS OF GLYCOSYLATED AND NONGLYCOSYLATED PROLACTIN ONISLET CELL-DIVISION AND INSULIN-SECRETION

A growing body of evidence suggests that prolactin (PRL) is a potent r egulator of the structure and function of the islets of Langerhans, bu t PRL is a polymorphic hormone that exists in several molecular forms. Therefore, it is important to know whether glycosylated PRL, a major structural variant of the hormone in several species, has an effect di fferent from that of the nonglycosylated PRL on islet function. This i n vitro study examined the differential effects of glycosylated and no nglycosylated porcine PRL on cell division and insulin secretion from neonatal rat islets, and compared these results with those produced by homologous rat PRL. The nonglycosylated porcine PRL produced modest s timulation of cell division and insulin secretion from rat islets, but glycosylated porcine PRL had no significant effects. The stimulations produced by nonglycosylated porcine PRL were much weaker in compariso n to those produced by the homologous rat PRL. The results show differ ential effects of the two structural variants of porcine PRL on rat is let function. Although these findings must be confirmed in a homologou s system, the results present the possibility that the structural form of the PRL molecule available to the islet tissue may be crucial for its normal functioning.