/sup 3/H-cyclosporine internalization and secretion by human fetal pancreatic islets

Journal Article · Sat Oct 01 04:00:00 EDT 1988 · Proc. Soc. Exp. Biol. Med.; (United States)

DOI:https://doi.org/10.3181/00379727-189-42782· OSTI ID:6582678

Formby, B; Walker, L; Peterson, C M

Human fetal pancreatic islets were isolated from 16- to 20-week-old fetuses by a collagenase technique and cultured 48 hr in RPMI 1640 containing 10% human adult serum and unlabeled 0 to 5 micrograms cyclosporine A (CsA)/ml. Insulin secretory capacity of human fetal islets was expressed as a fractional stimulatory ratio FSR = F2/F1 of the fractional secretion rates during two successive 1 hr static incubations first with 2 mM glucose (F1) to stabilize secretion followed by maximal stimulus, i.e., 25 mM glucose plus 10 mM L-leucine and 10 mM L-arginine (F2). Unlabeled CsA at the above concentrations had no significant effects on the insulin secretory capacity expressed by FSR-values. Studies of net uptake of 3H-CsA by islets cultured for varying periods up to 40 hr and expressed as picomole 3H-CsA per picomole islet insulin content demonstrated that uptake rate was slow and did not reach isotopic equilibrium over the 40 hr of culture. When isolated fetal islets were cultured for 48 hr in the presence of 3H-CsA and varying concentrations of unlabeled CsA it was found during two successive 1 hr static incubations that fetal islets secrete insulin concomitantly with 3H-CsA following maximal stimulus for secretion. An optimal secretory molar ratio of 3H-CsA to insulin of 4.0 +/- 1.3 (n = 7) was found after islets were cultured 48 hr in the presence of a saturating 2.128 micrograms 3H-CsA per milliliter culture medium. In three successive 30-min static incubations of 3H-CsA loaded islets, first with low glucose, followed by high glucose plus L-arginine and L-leucine, and finally with high glucose plus L-arginine and L-leucine and 10 mM theophylline, the proportional fractional secretion rates of insulin and 3H-CsA were of the same magnitude.

• Research Organization: Sansum Medical Research Foundation, Santa Barbara, CA (USA)
• OSTI ID: 6582678
• Journal Information: Proc. Soc. Exp. Biol. Med.; (United States), Journal Name: Proc. Soc. Exp. Biol. Med.; (United States) Vol. 189:1; ISSN PSEBA
• Country of Publication: United States
• Language: English

Related Subjects

550501* -- Metabolism-- Tracer Techniques
59 BASIC BIOLOGICAL SCIENCES
ALDEHYDES
ANIMALS
BIOCHEMICAL REACTION KINETICS
BODY
CARBOHYDRATES
DIGESTIVE SYSTEM
DRUGS
ENDOCRINE GLANDS
FETUSES
GLANDS
GLUCOSE
HEXOSES
HORMONES
IMMUNOSUPPRESSIVE DRUGS
INSULIN
ISOTOPE APPLICATIONS
KINETICS
LABELLED COMPOUNDS
MAMMALS
MAN
METABOLISM
MONOSACCHARIDES
ORGANIC COMPOUNDS
ORGANS
PANCREAS
PEPTIDE HORMONES
PRIMATES
REACTION KINETICS
SACCHARIDES
SECRETION
TRACER TECHNIQUES
TRITIUM COMPOUNDS
VERTEBRATES