VASOSTATINS, N-TERMINAL PRODUCTS OF CHROMOGRANIN-A, ARE RELEASED FROMTHE STIMULATED CALF SPLEEN IN-VITRO

Vasostatins are the N-terminal chromogranin A peptides 7 similar to 22 kDa. They have been shown to be present in several endocrine tissues and exhibit vasoinhibitory activity in vitro. In a first series of exp eriments, we investigated the presence and subcellular localization of vasostatins in the bovine splenic nerve. Experimental results, obtain ed using gradient centrifugation, showed that noradrenaline was enrich ed 25-fold in the large dense core vesicle fraction, compared with the original homogenate. In the latter fraction, the 7 and 18 kDa peptide s were observed following immunodetection with antiserum to chromogran in A(1-40) and laser densitometric scanning revealed these two fragmen ts as the major N-terminal fragments. Subsequently, we examined the re lease of the 7 and 18 kDa peptides from perfused calf spleen during ve ratridine (20 mu M) or 1,1-dimethyl-4-phenylpiperazinium iodide (20 mu M) stimulation. In the prestimulation samples, we were not able to de tect these peptides, however, following stimulation, the 7 and 18 kDa chromogranin A fragments became apparent. The vasostatin-immunoreactiv ity, in both bovine chromaffin granule lysate and calf spleen perfusat e, elutes at the same retention time on reversed-phase high performanc e liquid chromatography. The present study demonstrated that vasostati ns are present in the large dense core vesicles of sympathetic axons a nd are released from the nerve terminals in response to stimulation. T he release of vasostatins from sympathetic nerves in the spleen sugges t an in vivo function for N-terminal chromogranin A products of neuron al origin.