Occurrence, storage and release of neurotensin-like immunoreactivity from the adrenal gland

Abstract

In the present study we have investigated the presence of radioimmunoassayable neurotensin-like immunoreactivity (NTLI) in extracts of adrenal glands from hen, guinea-pig, rat, cat, dog and man. In addition, gel filtration chromatography and studies on the storage site of NTLI, using subcellular fractionation techniques, were performed. Finally, NTLI release in relation to noradrenaline (NA) from cat adrenal glands upon splanchnic nerve activation was studied in vivo. In all species investigated except guinea-pig and man, the NTLI levels in the adrenal glands were higher than the levels in the heart (control tissue) but lower than in the ileum. Gel filtration of NTLI from cat adrenal glands revealed presence of roughly equal amounts of the whole neurotensin molecule, i.e. NT(1-13), and its main metabolite the N-terminal octapeptide NT(1-8), while in plasma from the adrenal vein almost exclusively NT(1-13) was revealed after electrical stimulation of the splanchnic nerve. The release of NTLI and NA upon splanchnic stimulation was antagonized by hexamethonium. Subcellular fractionation of cat adrenal glands indicated that NTLI was stored in a large subcellular organelle, co-migrating with chromaffin granules. We suggest that NT may be a new adrenal gland hormone or transmitter, possibly co-stored with NA in chromaffin cells. However, at the present stage it cannot be distinguished whether NT exerts its actions locally within the adrenal gland or after release into the systemic circulation.