In older men, pathways occurred from chronic stress to distress to the metabolic syndrome, which in turn predicted CHD. Older women not using HRT showed fewer pathways than men; however, over time, distress, the MS, and CHD were related. No psychophysiological pathways occurred in older women using HRT.

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In humans, matching of heat loss and heat production in the "neutral" zone, defined operationally in terms of a range of skin temperatures (Tsk), is accomplished by regulation of skin blood flow (SkBF). Our studies were designed to reveal the characteristics of control of SkBF [from measurements of forearm blood flow (FBF)] in this zone. We controlled the temperature of water sprayed on most of the body of supine men and women at 33 or 35 degrees C in a square-wave pattern (15 min at each temperature) or a step pattern (60 min at 33 degrees C separated by short periods at 35 degrees C). FBF followed Tsk (0.5 ml.min-1.degrees C-1). Esophageal temperature changed approximately 0.11 degrees C with each 2 degrees C change in Tsk, falling with Tsk increase and vice versa. Little influence on FBF, < 0.1 ml.min-1.100 ml-1. degrees C-1, was observed when only the forearm was sprayed with 33 and 35 degrees C water. We conclude that SkBF control in the 33-35 degree C range of Tsk is dominated by the feedforward reflex influence of Tsk on SkBF. The reflex response overcompensates for the effect of Tsk on thermal balance in the neutral zone, so that equilibrium core temperature has an inverse relationship to Tsk.

It was previously shown that red blood cells release ATP when blood oxygen tension decreases. ATP acts on microvascular endothelial cells to produce a retrograde conducted vasodilation (presumably via gap junctions) to the upstream arteriole. These observations form the basis for an ATP hypothesis of local metabolic control of coronary blood flow due to vasodilation in microvascular units where myocardial oxygen extraction is high. Dogs (n ϭ 10) were instrumented with catheters in the aorta and coronary sinus, and a flow transducer was placed around the circumflex coronary artery. Arterial and coronary venous plasma ATP concentrations were measured at rest and during three levels of treadmill exercise by using a luciferin-luciferase assay. During exercise, myocardial oxygen consumption increased ϳ3.2-fold, coronary blood flow increased ϳ2.7-fold, and coronary venous oxygen tension decreased from 19 to 12.9 mmHg. Coronary venous plasma ATP concentration increased significantly from 31.1 to 51.2 nM (P Ͻ 0.01) during exercise. Coronary blood flow increased linearly with coronary venous ATP concentration (P Ͻ 0.01). Coronary venous-arterial plasma ATP concentration difference increased significantly during exercise (P Ͻ 0.05). The data support the hypothesis that ATP is one of the factors controlling coronary blood flow during exercise. It has long been known that ATP is a powerful coronary dilator (8). Studies by Wolf and Berne (25) and Moir and Downs (16) demonstrated that ATP is more potent than adenosine in producing coronary vasodilation. Bergfeld and Forrester (1) observed that human red blood cells release ATP under hypoxic conditions. Ellsworth and colleagues (6, 7) demonstrated a progressive release of ATP from hamster red blood cells during declines in oxygen tension. They used oxygen tensions of ϳ35 and ϳ11 mmHg and maintained a constant pH (7.36) and carbon dioxide tension (35 mmHg). Thus ATP release from red blood cells took place during physiological declines in oxygen tension without the interaction of carbon dioxide or pH.Once released from the red blood cell, ATP acts on endothelial cell purinergic receptors (12,19). The injection of ATP inside small arterioles (5, 7, 15), outside capillaries (7), or inside venules (3) results in a retrograde conducted response that dilates the upstream feed arteriole. Duling and colleagues (9, 21) demonstrated that responses caused by several agonists are conducted along microvascular endothelial cells via gap junctions to the upstream feed arterioles. The assumption is that the conducted response due to ATP is also mediated via gap junctions. The relaxation of the feed arteriole increases oxygenated blood flow where oxygen extraction is high. Through its ability to release ATP in areas of low oxygen tension, the red blood cell may serve as a regulator of coronary blood flow during increases in myocardial oxygen consumption.The purpose of the current study was to test the ATP hypothesis in the coronary circulation during exercise. The major results of the present s...