Dynamic 131I-labelled insulin distribution in rabbits as seen by in-vivo scintigraphic studies.

The kinetics of 131I-labelled insulin distribution in heart, liver, kidneys and urinary bladder of rabbits were studied in vivo by gamma-camera techniques combined with plasma measurements (glucose concentrations and chromatographic separation of insulin and its degradation products). The distribution space of radioiodinated insulin differed from the vascular bed delineated by radioiodinated serum albumin. During a 20-min gamma-camera recording, radioactive degradation products only appeared in the plasma after 10-12 min.

alpha-Melanocyte-stimulating hormone binding and biological activity in a human melanoma cell line.

Synthetic alpha-melanocyte-stimulating hormone (alpha-MSH) was found to bind to the plasma membrane of the HM6A human melanoma cell line, using an immunocytochemical method. When treated with 10(-7) to 10(-9) M alpha-MSH, melanoma cells exhibited an increase of intracellular cyclic adenosine 3':5'-monophosphate, followed by stimulation of tyrosinase activity. Significant inhibition of DNA synthesis measured by [3H]thymidine uptake and inhibition of cell growth was found.