FLOW CALORIMETER FOR ASSAY OF HORMONE-INDUCED AND METABOLITE-INDUCED CHANGES IN STEADY-STATE HEAT-PRODUCTION BY TISSUE

A compact, heat conduction, flow calorimeter for use in monitoring tissue response to metabolic regulators has been designed and constructed. The instrument operates as a perfusion apparatus. Heat production by tissue can be measured continuously, and nutrient and oxygen concentrations can be kept at optimum, constant levels. Introduction of substances of interest is made without production of attendant thermal mixing artifacts. The resolution time of events is less than 10 s. The thermal stability of the instrument is maintained by dynamic methods. The sensitivity of the instrument, 7.2 μW/μV, allows observation of changes in heat production as small as 3 × 10-4 to 5 × 10-4 cal/min, the equivalent of 3-5% of the heat production of a representative 1-g quantity of fresh tissue. The calorimeter was used to monitor changes in the steady-state heat production of 250-mg samples of corn coleoptile tissue in response to the plant growth substance, indoleacetic acid. © 1979.