Differential effects of glycosylated and nonglycosylated prolactin on islet cell division and insulin secretion.

A growing body of evidence suggests that prolactin (PRL) is a potent regulator of the structure and function of the islets of Langerhans, but 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 different from that of the nonglycosylated PRL on islet function. This in vitro study examined the differential effects of glycosylated and nonglycosylated 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 stimulation 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 comparison to those produced by the homologous rat PRL. The results show differential effects of the two structural variants of porcine PRL on rat islet function. Although these findings must be confirmed in a homologous 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.