APStracts 3:0051C, 1996.

Dipeptide uptake by adenohypophyseal folliculo-stellate cells. Otto, Christiane, Susanne Tom Dieck, and Karl Bauer. Max-Planck-Institut f[umlaut]ur Experimentelle Endokrinologie Hannover, F.R.G.

APStracts 3:0051C, 1996.

Dipeptide uptake was studied in primary cultures from rat anterior pituitaries by use of radiolabeled carnosine and the fluorescent dipeptide derivative [beta]-Ala-Lys-Ne-AMCA (AMCA= aminomethylcoumarin acetic acid). Fluorescence microscopic studies revealed that the reporter peptide specifically accumulated in the S -100 positive folliculo-stellate cells which do not produce any known hormone. The dipeptide derivative was taken up in unmetabolized form by an energy-dependent, saturable process with apparent kinetic constants of Km = 19 [mu]M and Vmax = 5.5 nmol/mg protein x h. This high affinity transporter was strongly affected by inhibitors of sodium proton exchangers and thus appeared to be driven by a proton gradient. Competition studies revealed that the peptide transporter exhibits broad substrate specifity with a preference for hydrophobic dipeptides. In contrast to free amino acids and the pseudotetrapeptide amastatin, tripeptides were also accepted. Compounds without an [alpha]- or [beta]- amino group such as captopril, thiorphan and benzylpenicillin did not affect uptake of the reporter peptide, although being substrates of the well characterized intestinal and renal dipeptide transporters.

Received 11 October 1995; accepted in final form 22 January 1996.
APS Manuscript Number C616-5.
Article publication pending Am. J. Physiol. (Cell Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 8 February 96