The Calculation of Transfer Rates in Two Compartment Systems Not in Dynamic Equilibrium

Abstract

Dynamic equilibrium in a biological system implies that the compartment under study does not change in size during the period of observation. In many biological systems there are, however, net changes with time and this report deals with the mathematical treatment necessary to calculate unequal rates of inflow and outflow.A method is presented for the calculation of transfer rates in a two compartment system when the rates of flow between these compartments are unequal but constant. Equations were developed to calculate the amount of material transported per unit time derived from measurements of specific activity and compartment size.

Effects of vasoactive intestinal polypeptide on intestinal absorption and blood flow.

“…The effluent was collected and 3H, 14C and 22Na measured by liquid scintillation counting. Net and unidirectional Na and H2O fluxes were calculated by the method of Berger & Steele (1958). Na was determined by flame photometry.…”

The effect of deoxycorticosterone on the undirectional transfers of sodium and potassium into and out of the dog intestine

“…Transfer rates were calculated for two compartment systems not in dynamic equilibrium (Berger & Steele, 1958). The following equations were used:…”

“…The specific activity of the plasma may be neglected for potassium (OA > OB) and, except where radiosodium was administered intravenously, for most experiments specific activity of plasma sodium may also be neglected (Berger, Kanzaki, Homer & Steele, 1959). Further details of the method are described in previously published work (Berger & Steele, 1958;Berger, Kanzaki, Homer & Steele, 1959;.…”

Intrinsic regulation of functional blood flow and water absorption in canine colon.

“…Unidirectional H20 fluxes were calculated by the method of Berger & Steele (1958). These techniques have been presented in detail elsewhere (Mailman & Jordan, 1975).…”