[Effects of chronic hypoxia on calmodulin activity in rats].

To investigate the effects of chronic hypoxia of calmodulin activity in rats, we divided 40 wistar rats into four major groups. One group acted as control. The other three groups were made hypoxic by placing them in an isobaric hypoxic chamber (O2 = 10%) for 1, 2 and 3 weeks respectively. Calmodulin activity was measured by Phosphodiesterase method. The results showed that the mean pulmonary arterial pressure and the pulmonary vascular resistance in rats were remarkably increased by chronic hypoxia. The total calcium levels and the calmodulin content in the lung tissue of rats were significantly elevated at 2-3 weeks of hypoxia exposure. However, the calmodulin content in the lung tissue of the rats exposed to hypoxia for 1 week also increased, but it was lower than those at 2-3 weeks of hypoxia exposure. Therefore, we conclude that Ca(2+)-calmodulin system may play a central role in mediating hypoxai-induced pulmonary hypertension.