AGE AND THE CALORIGENIC RESPONSE TO SUBCUTANEOUSLY ADMINISTERED ADRENALIN IN THE RAT

Abstract

Subcut. inj. of adrenalin (0.02 mg. per 100 gs. body wt.) in [male], albino rats, 2-28 mos. old, causes an avg. maximal increase in O2 consumption of 34.5% within 45 mins. after inj.; thereafter there is gradual decline to a value still about 5% above the preliminary basal figure 4 hrs. after inj. R. Q. increases from an avg. basal value of 0.72 to 0.79 within 15 mins. after inj.; from this maximum it declines to normal within 75 mins. and continues to decrease to approx. 0.67 which is reached within 150 mins. and is maintained with only slight tendency toward recovery until the end of the 4-hr. period. The total avg. increase in O2 consumption for the 4-hr. period is 19.5%; the preliminary increase in R. Q. is so nearly balanced by the compensatory fall that the total value for the 4-hr. period is practically unchanged from the preliminary normal. In the older rats the maximum increase in O2 consumption is less and is delayed until 90 mins. after inj.; the maximal increase in R. Q. is practically the same and is reached at about the same time in all age groups, but the return to normal seems significantly delayed in proportion to increasing age. A delay in the absorption of the subcutaneously injected adrenalin proportional to age is tentatively suggested as a possible cause of these effects.