Time course of pulmonary vasoconstriction with repeated hypoxia and glucose depletion

Hypoxic Pulmonary Vasoconstriction

“…Thus precontraction may restore an initial level of intrinsic tone necessary for expression of HPV. In some studies where prestimulation was not required, hypoxic responsiveness may have been promoted by particular experimental conditions, such as absence of glucose (1417,1818) or bicarbonate and CO 2 (2175) in the bathing media, and "adaptation" of vessels by continuous exposure to hypoxia for 4 -6 h before hypoxic challenges (799). In others, hypoxic responses were present but much smaller and more variable than responses in precontracted vessels (393,413,1652).…”

“…At durations Յ20 min in rats (1413,1651,1652,1691,1715,1767,2185) and Յ30 min in other species, including cow (1430), dog (375, 429), ferret (2089), guinea pig (1818), human (394, 815), pig (1282,1976), rabbit (399, 903,1417), and sheep (392, 393, 1959 -1961), severe hypoxia caused either vasoconstriction or vasoconstriction followed by vasodilation, perhaps representing partial or complete phase 1 responses, respectively. As with phase 1 during prolonged hypoxia, these responses were occasionally preceded by a brief vasodilation (506, 656,876,1151,1207,1208).…”

“…Its effects on crossbridge cycling are partly related to the fact that dissociation of P i from the actinmyosin complex is the rate-limiting step in turnover of smooth muscle crossbridges (69), and a reduction in cytosolic [P i ] is associated with increased tension in systemic arteries (746). Like [PCr], phosphorylation potential declines less in pulmonary than systemic arteries during hypoxia, as long as glucose is available (1045,1417), suggesting that energy state is better controlled in pulmonary arteries during hypoxia, due in part to enhanced glycolysis (1042,1044,1045).…”

“…Easier dissection and mounting probably explains why most investigators have chosen to study proximal (orders 1-5) rather than distal (orders 6 and greater) pulmonary arteries, where main, right or left, lobar, segmental, and subsegmental arteries represent orders 1, 2, 3, 4, and 5, respectively. 799,991,1045,1282,1976), rabbit (197,198,399,413,903,1417), rat (60, 126, 139, 412, 436, 656, 896, 899, 900, 908, 909, 934, 935, 1018, 1038, 1041, 1043, 1056, 1131, 1207, 1208, 1413, 1474, 1638 -1642, 1651, 1652, 1691, 1715, 1767, 1894, 1896, 1905, 1934, 2018, 2175, 2185, 2190, 2206 -2208), and sheep (392, 393, 1959 -1961). While some investigators were able to elicit contractile responses to hypoxia under basal conditions (4, 392-394, 412, 413, 799, 1417, 1652, 1715, 1818, 2175), most found that exposure to a contractile stimulus before and during hypoxia was required to obtain measurable, reproducible responses in this preparation.…”

Slow and fast changes in transmural pulmonary artery pressure in obstructive sleep apnoea

“…However, our findings may be explained on the basis of the well-known time course of the pulmonary vessels response to hypoxia, which is slower than SaO 2 changes during apnoeic cycles. In fact, hypoxic pulmonary vessel response starts within a few seconds of exposure to hypoxia but peaks only after some minutes [10][11][12][13][14]. SaO 2 falls during sleep apnoeas are generally produced in less than a minute, and are reverted in only a few seconds.…”