EFFECTS OF PEPTIDE-T DERIVATIVES ON THE PROLIFERATION OF CULTURED HUMAN KERATINOCYTES

[D-Ala(1)]peptide T-amide, the linear hexapeptide H-Thr-Hse-Asn-Tyr- A sp-OH (LPT) and its cyclic analog, cyclo(- Thr-Hse-Asn-Tyr-Thr-Asp-) ( CPT), were tested for their effects on the proliferation of cultured n ormal human keratinocytes (KTs) in comparison with vasoactive intestin al peptide (VIP). [D-Ala(1)]PT-NH2, LPT and VIP (all 0.1 mu mol/l) inc reased the cell number in KT cultures, whereas CPT was ineffective. Th e VIP antagonist [N-Ac-Tyr(1),D-Phe(2)]GRF (1-29)-NH2 significantly in hibited the VIP effects on KTs. On the other hand this antagonist did not affect the peptide T (PT) compounds-induced stimulation of KTs, pr oviding indirect evidence that the mitogenic effects of VIP and PT pep tides are probably mediated via different receptors.