Date of Award

Summer 1967

Document Type

Thesis

Degree Name

Master of Science

Department

Biology

Abstract

Presently, the theory is held that the total frog skin potential (P.D.) is generated within the epidermis at two borders, the "outer border" and the "inner border, " which are said to be specifically permeable to Na+ and K+, respec­tively. This thesis concerns itself only with the electrical response of the "outer border" to varying Na+ concentrations in the solutions at the epidermis, [Na+]o. Contrary to expectation from the Nernst equation, the P.D. changes by only 17 to 35 mV, instead of theoretically 58 mV upon a 10 fold change in [Na+]o. This paper shows that it is very unlikely that the discrepancy between theory and experiment results from the participation of movement of K+, H+, and S04= across the "outer border" which indeed, seems to be specifically permeable to Na+. Results for epinephrine treated skins suggest that this Na+ specificity is complete­ly lost. A theoretical treatment of the mechanism of generation of the "outer border" skin P. D., presented in this thesis, shows that the difference between theory and experiment can be explained if two factors are added to the concept that the "outer border " skin P. D. is a Na+ diffusion potential. These factors are: 1) Continuous active transport of Na+ across the skin, and 2) Diffusion delay within the epidermis in the layers in front of the "outer border." Taking these two factors into account, a modified Nernst equation was derived to show the dependence of' the skin P. D. on varying [Na+]o. It is given by Equation (I8) in the list of Equations. A test for this equation shows that it adequately describes the response of tho epidermis of the frog skin to varying Na+ concentration at the epidermal side of the skin.

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