BIOCHEMICAL DETECTION AND IMMUNOHISTOCHEMICAL LOCALIZATION OF ENKEPHALIN-LIKE SUBSTANCES IN PERIPHERAL-TISSUES OF THE SCALLOP PECTEN-MAXIMUS (LINNAEUS)

This study focused on the biochemical detection of the methionine-enke phalin-, leucine-enkephalin-and methionine-enkephalin-arg-gly-leu-like peptides in the stomach, digestive gland, male and female gonads, mus cle, gill and mantle of the scallop Pecten maximus using specific radi oimmunoassays. Enkephalin-like substances were mainly present in the s tomach and in the digestive gland, where leucine-enkephalin-and methio nine-enkephalin-arg-gly-leu-like peptides were the predominant of thes e substances. In the gonads, muscle, gill and mantle, the enkephalin-l ike contents were close to the sensitivity threshold of the enkephalin antibodies. The enkephalin-like contents measured in September, in th e digestive complex, were significantly higher than in December, when the bivalves have undergone a period of starvation. Immunohistochemica l assays were performed on the stomach and the digestive gland to loca lize the enkephalin-like materials. In these organs, which are the mai n sites of the digestive process in Bivalvia, the enkephalin-like mate rials were mainly confined to the endocrine-like cells. These results suggest that in Pecten maximus, opioids may be involved in the digesti ve processes mainly through enkephalin-endocrine-like cells.