| Fernández-Durango showed that intracamerally injected BNP stimulated guanylate cyclase activity and decreased IOP. Under chronic hypoxic conditions, plasma levels of BNP have been found to increase. In addition to extended exposure to hypobaric hypoxia itself (10-91 days), endurance training in hypobaric hypoxic conditions leads to a marked early increase in ventricular and atrial BNP mRNA levels. As for the physiologic effects that can be produced by elevated plasma BNP levels, Klinger et al., found that in rats, BNP infusion attenuated the development of hypoxic pulmonary hypertension. The authors suggested that this finding supports the hypothesis that endogenous BNP plays a role in modulating the pulmonary hypertensive responses seen in chronic hypoxia.