[Systemic and regional hemodynamics in alert rats with increasing hyperthermia]. / Sistemnaia i regionarnaia gemodinamika u bodrstvuiushchikh krys v usloviiakh narastaiushchei gipertermii.

The changes in the parameters of systemic and regional hemodynamics during thermal stress were followed up in awake male Wistar rats. The cardiac output (CO) and blood flow in 16 zones of the body were measured by means of 15 microns microspheres labeled by 4 different isotopes. The blood flow increased in the skin of the tail, the liver, heart, adrenals, and skeletal muscles and reduced in the organs of the splanchnic region and kidneys. When body temperature reached 42 degrees C the CO decreased. The shifts in the regional blood flow maintained their direction, with the exception of a sharp increase of blood flow in the small intestine which preceded or coincided with the beginning of a fall in arterial pressure. The rate of increase of left ventricular pressure remained at a high level. It is assumed that the disruption of celiac vasoconstriction is among the earlier developing links of hemodynamic disorders in thermal affections and is caused by the vasodilative effect of the factors of local control of the vascular functions.

[Differences in the redistribution of cardiac output during hyperthermia in waking rats and guinea pigs]. / Razlichiia v pereraspredelenii serdechnogo vybrosa pri gipertermii u bodrstvuiushchikh krys i morskikh svinok.

The heat stress induced common responses in rats and guinea pigs: an increase in the blood flow at the sites of heat radiation and in the diaphragm, and its decrease in splanchnic area's organs and in kidneys while cardiac output remained constant. The species differences occurred in the responses of intestine and skeletal muscles' vessels. The differences seem to be due mainly to the differences in behavioral responses to the heat stress in these animals.