HETEROGENEITY STUDIES OF HAMSTER CALCITONIN FOLLOWING ACUTE EXPOSURE TO CIGARETTE-SMOKE - EVIDENCE FOR MONOMERIC SECRETION

Various acute stimuli, including cigarette smoke, induce hypercalciton emia in man and hamsters. We have shown that this occurs also in thyro idectomized subjects. In the present study we have further explored th is phenomenon of secretion from the lungs by studying, simultaneously, the HPLC characteristics of pulmonary tissue and serum in control ham sters and in animals immediately following short-term exposure to ciga rette smoke. In addition, we have studied the immunoheterogeneity of l ung calcitonin 24 hours following the acute exposure. Control lungs co ntained monomeric immunoreactive calcitonin (M-iCT), high molecular ma ss iCT (H-iCT), and CT fragments. Immediately following smoke exposure , there was an acute decrease of lung iCT by radioimmunoassay (RIA) wh ich consisted primarily of a decrease in M-iCT by HPLC. Simultaneously , the iCT increase in the serum by RIA was shown by HPLC to involve M- iCT. Twenty-four hours after smoke inhalation, the lung iCT by RIA and M-iCT by HPLC had returned towards control levels. These findings doc ument the molecular characteristics of lung iCT following acute cigare tte smoke stimulation, and suggest that under certain circumstances M- iCT may be actively secreted by the lung. It remains to be determined whether this type of secretion reflects hemocrine or paracrine release and what the physiological role for such a secretion may be.