ESTIMATION OF THE FILTRATION CONSTANT OF DOG SUBMAXILLARY GLAND EPITHELIA

To estimate the hydraulic conductivity of dog submaxillary gland, an attempt was made to determine filtration constants of the glandular epithelium by analyzing the decay curve of the stop-flow intraluminal pressure.The time course of the decay of intraluminal pressure after cessation of the secretory stimulation was found to be expressed as an algebraic sum of two exponential functions of time, one having the rapid component and the other having the slow component:P=Ae-λ1t+Be-λ2tThe rapid component is atributable to the relaxation of the myoepithelium because the rate constant of the rapid component (λ2) is in good accordance with the rate constant of the relaxation of the myoepithelium. The rate constant of the slow component (λ1) is deduced theoretically to be a product of the filtration constant and a coefficient of volume elasticity of the gland. The value of λ1, was found experimentally to be 0.00512 sec-1, and the coefficient of volume elasticity obtained by measuring the intraluminal pressure elevated by retrograde injections of fluid was 1.52 mmHg·g-gland·μl-1. From these results, the filtration constant of dog submaxillary gland was estimated to be 0.0033 μl·sec-1·mmHg-1·g-glamd-1 on the average. Recalculating the value on the basis of the surface area of the acinus per unit gland weight, a value of the filtration constant or an approximate value of the hydraulic conductivity of the acinal surface was calculated to be 0.6×10-11 cm3·sec-1·dyne-1. The numerical values of the parameters described above may be applicable under similar experimental conditions to those used in the present study.