title: Prolactin (in vitro) decreases the glucose stimulation threshold, enhances insulin secretion, and increases dye coupling among islet B cells.
abstract: The purpose of this study was to determine the in vitro effect of ovine PRL (oPRL) on the dynamics of insulin secretion and dye coupling among islet B cells. The effect of oPRL (2 micrograms/ml) on insulin secretion was time dependent and reached a maximum on day 4 when there was a 2.4-fold increase in insulin secretion from cultured neonatal rat islets (n = 6, P less than 0.001). When islets cultured in the presence of oPRL for 4 days were perifused, 300 mg/dl glucose stimulation resulted in insulin release of 131 +/- 20 microU/ml.100 micrograms islet tissue as compared to control islets 94 +/- 20 microU/ml.100 micrograms islet tissue (n = 7, P less than 0.02). Stimulation of the islets with a linear 30-250 mg/dl glucose gradient resulted in a threshold for glucose-stimulated insulin secretion of 73 +/- 6 mg/dl glucose for the oPRL treated islets (n = 7) as compared to a threshold of 123 +/- 6 mg/dl glucose for control islets (n = 7, P less than 0.001). Mean islet volume was unchanged after 4 days of oPRL treatment but was 34% greater after 8 days (n = 6, P less than 0.001). Dye coupling among central islet B cells was also increased after in vitro treatment with oPRL for 4 days. The mean projected area of dye spread was 2-fold greater in the oPRL treated islets (n = 33) in comparison to the control islets (n = 33, P less than 0.05). These results indicate that in vitro lactogen treatment, in the form of oPRL, alters insulin secretory behavior and B cell junctional communication and supports our hypothesis that lactogen, insulin secretion, and junctional communication among B cells are related.
authors.affiliation: Department of Cell Biology and Neuroanatomy, University of Minnesota, Minneapolis 55455.
authors.forename: R L
authors.initials: RL
authors.lastname: Sorenson
authors.forename: T C
authors.initials: TC
authors.lastname: Brelje
authors.forename: O D
authors.initials: OD
authors.lastname: Hegre
authors.forename: S
authors.initials: S
authors.lastname: Marshall
authors.forename: P
authors.initials: P
authors.lastname: Anaya
authors.forename: J D
authors.initials: JD
authors.lastname: Sheridan
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D004247:DNA / Q000378:metabolism; D004056:Differential Threshold; D005947:Glucose / Q000494:pharmacology*; D007328:Insulin / Q000378:metabolism*; D000078790:Insulin Secretion; D007515:Islets of Langerhans / Q000166:cytology / Q000378:metabolism*; D007546:Isoquinolines / Q000378:metabolism*; D011388:Prolactin / Q000494:pharmacology*; D051381:Rats; D011916:Rats, Inbred F344; D013268:Stimulation, Chemical; D013997:Time Factors
chemical_list: D007328:Insulin; D007546:Isoquinolines; D011388:Prolactin; D004247:DNA; C017475:lucifer yellow; D005947:Glucose