PROCTOLIN-LIKE PEPTIDE IN CRAB PERICARDIAL ORGANS

Evidence is presented that one of the cardio‐excitatory peptides known from crab pericardial organs is identical to or a close analog of proctolin, a putative peptide‐transmitter in insects. Acid ethanol extracts of crab pericardial organs contain a cardioexcitatory peptide which is pharmacologically and chromatographically indistinguishable from proctolin. The peptide exhibits an apparent molecular weight of approximately 600 as determined by gel filtration, is not degraded by trypsin but readily inactivated by leucine aminopeptidase. Application of this decapod cardioexcitatory peptide to the cockroach gut effects a dose‐dependent contracture identical to that produced by proctolin. Similarly, proctolin elicits a characteristic inotropic response from crab hearts. Copyright © 1979 Wiley‐Liss, Inc., A Wiley Company