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CHANGES IN THE METABOLISM OF THE SHIVERING HIND LEG OF THE YOUNG OX DURING SEVERAL DAYS OF CONTINUOUS COLD EXPOSURE
Author(s) -
Bell A. W.,
Clarke P. L.,
Thompson G. E.
Publication year - 1975
Publication title -
quarterly journal of experimental physiology and cognate medical sciences
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.925
H-Index - 101
eISSN - 1469-445X
pISSN - 0033-5541
DOI - 10.1113/expphysiol.1975.sp002321
Subject(s) - shivering , zoology , chemistry , hindlimb , leg muscle , medicine , endocrinology , blood flow , oxygen , biology , surgery , organic chemistry , physical medicine and rehabilitation
The effect of 4 days of continuous exposure to a cold environment on blood flow in, and oxygen and energy substrate uptake by the shivering hind leg has been studied in young steers. The animals shivered throughout the period of cold exposure and total oxygen consumption (total Vo 2 ) remained 40—50% greater than Vo 2 during thermoneutrality. Leg blood flow (leg Q) and oxygen uptake (leg VO 2 ) increased two‐ and four‐fold respectively on the first day of cold. Both had declined significantly by the final day, leg Q to a level 37% greater than, and leg VO 2 , to about double, pre‐cold levels. The change in the relationships of leg Q and leg Vo 2 to total Vo 2 was examined by linear regression analysis, which suggested that the changing contribution of leg VO 2 to total Vo 2 was entirely due to changes in leg Q, rather than in the arteriovenous difference in blood oxyhaemoglobin saturation across the leg. The net uptakes by the leg of free fatty acids (FFA), acetate, glucose and lactate all increased on the first day of cold. Both glucose and acetate uptakes were greater on day 4 than on day 1 in the cold, in spite of the lower leg Vo 2 , but net uptakes of FFA and lactate were considerably lower. The decrease in net uptake of FFA is attributed mainly to an increase in the rate of lipolysis and release of FFA from fat depots in the leg, because of the associated progressive increase in the release of glycerol and oleic acid from the leg. The molar ratios of net carbohydrate substrate, acetate and FFA uptakes to leg Vo 2 are compared. The results suggest that tissues other than the leg muscles become increasingly important as sites of heat production, and that there are changes in the utilization of glucose, acetate and FFA by shivering muscle, during prolonged cold exposure.