Degree Name

PhD (Doctor of Philosophy)

Program

Biomedical Sciences

Date of Award

May 1994

Abstract

A role for protein kinase C (PKC) in the denervation-induced supersensitivity of the rat vas deferens was investigated. Chronic, surgical denervation of the rat vas deferens (up to 8 days) resulted in tissues that produced enhanced contractile responses to norepinephrine (NE) in isolated organ baths. Single challenges of NE (10 $\mu$M) produced 0.6 $\pm$ 0.1 g of maximal tension in the control vas whereas in the paired, denervated tissue 2.2 $\pm$ 0.3 g of tension was recorded (n = 6). Cumulative concentration-effect curves to NE produced in the denervated vas deferens were shifted 18-fold to the left of the control response. Neurokinin A (NKA) responses after denervation of the tissue were not significantly different from the control. Denervation did not alter the contractile response to phorbol diacetate (PDA), a PKC activator. Pretreatment of denervated and control vas deferens with 100 $\mu$M nifedipine (a calcium channel blocker), significantly attenuated the contractile response to NE. The responses in the control tissues were depressed by 88%, those in the denervated vasa were only antagonized by 65% after nifedipine treatment. Exposure of denervated and control vas deferens to 100 $\mu$M NE resulted in no significant accumulation of diacylglycerol (DAG) from basal values. The molecular species of DAG produced after receptor stimulation, in either tissue group, were not different from those found in resting tissues. Denervation also had no effect on the binding characteristics of membrane-associated PKC when assayed using the specific ligand, ($\sp3$H) phorbol dibutyrate. The PKC activity of resting vas deferens was not altered by chronic surgical denervation. Denervated and control vas deferens that were stimulated with 100 $\mu$M NE showed a time-dependent translocation of PKC from the cytosolic to the membrane fraction of the tissue. In both tissue groups exposure to NE resulted in a 3-4 fold increase in the membrane-bound PKC activity, which remained elevated above basal values for up to 20 min. The rate of translocation of PKC was faster in denervated vasa (maximal at 5 min after NE) when compared to the control (maximal at 20 min), but the maximal amount of the enzyme activated was the same for the two tissue groups. The ability of NKA, 60 mM K$\sp+$-depolarization and PDB (PKC activator) to produce translocation of the PKC was not altered by denervation of the vas deferens. (Abstract shortened by UMI.)

Document Type

Dissertation - Open Access

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