Date of Award

7-1-1987

Degree Type

Thesis

University or Center

Atlanta University (AU)

School

School of Arts and Sciences

Degree Name

M.S.

Department

Biology

First Advisor

Dr. Irene V. Brown

Abstract

Modulation of mouse epidermal gap junctions and differentiation in response to a natural retinoid, retinyl palmitate (RP), was evaluated. This is the first report of gap junction isolation and partial protein characterization from normal or retinoid-treated epidermis. Adult male Swiss Webster mice received parenteral injections of 13,750 International Units (IU) of RP for 12 days. Skin specimens were excised and analyzed by transmission electron microscopy (TEM) for morphologic changes in gap junctions and the epidermis. Gap junction proteins were isolated by discontinuous sucrose gradient centrifugation, following suspension in sodium bicarbonate buffer and, subsequent, solubilization in sarkosyl. Samples were analyzed by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). Verification of the reliability of the epidermal gap junction isolation procedure was ascertained in corollary liver studies using the standard protocol. Each isolation step was monitored by TEM. The ultrastructural results revealed an increase in the number of gap junctions in retinoid-treated epidermal specimens. Keratinization and keratinocyte differentiation were inhibited as reflected in. a decrease in the number of tonofilaments in keratinocytes and the subsequent suppression of stratum corneum formation. Analyses of isolated epidermal gap junction proteins by SDS-PAGE indicate four distinct bands ranging in molecular weight of 30-20 kilodaltons. Retinyl palmitate-treated samples are distinguished by enhanced gel profiles. Isolated epidermal connexin has a relative molecular weight of 30,000 daltons in samples from both treated and control specimens. The data suggest a positive role of gap junctions in retinoid-directed metabolic cooperation in the regulation of epidermal differentiation. These studies will form the basis for further investigations to determine if the intercellularly exchanged molecules, retinoids,induce requisite molecular alterations in gap junctions during epidermal differentiation. An understanding will be gained of the independent and/or collaborative mechanism(s) of action of retinoids and gap junctions in epithelia.

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