PubMed Health⌕ Search

Biomedical subjects

P A Longhurst

Publications and source records attributed to P A Longhurst.

95 records · Page 6Linked to original sources
PubMed1979

Effect of isoproterenol on phosphorylase activation in the hyperthyroid rat heart.

Pretreatment of rats for 3 days with triiodothyronine produced an increase in rate in the right atrium and a decrease in force of contraction in the right ventricle and Langendorff heart. Isoproterenol administration produced a time-dependent increase in rate and tension. The increase in rate was consistently greater in atria from hyperthyroid rats, and the increase in tension consistently greater in tissues from euthyroid rats. Isoproterenol also produced a time- and dose-dependent increase in phosphorylase a activity. In the isolated atria and ventricles enzyme activity was similar in the two groups. In the Langendorff hearts, however, there was an enhancement of the isoproterenol-induced increase in phosphorylase activity in hearts from hyperthyroid rats. Reduction of the coronary blood flow to the level found in euthyroid animals did not reduce the potentiation of phosphorylase activation found in hearts from hyperthyroid rats. It is concluded that the potentiation of phosphorylase activation in hearts from hyperthyroid rats is not due to the increase in coronary blood flow.

Animals↗
PubMedDate not supplied

Metabolic studies on the rabbit corpus cavernosum.

Erectile function (erection and detumescence) involves the complex interaction of direct neuronal stimulation of corporal smooth muscle, neurohumoral release of specific endothelial contractile and relaxant factors, and secondary modulation by a variety of putative neuropeptides and vasoactive modulators. The net result is a rapid and sustained relaxation of the smooth muscle elements during erection and contraction of the smooth muscle during detumescence. Proper function of the corporal tissue is dependent upon cellular metabolism of glucose and the generation of cellular energy in the form of high energy phosphates. The current study characterizes the following metabolic parameters of the rabbit corpus cavernosum: Tissue concentrations of creatine phosphate (CP), ATP, ADP, and AMP; maximal rate of glucose metabolism to lactic acid and CO2; and activities of the enzymes creatine kinase (CK), citrate synthase, and malate dehydrogenase. For comparative purposes only, bladder smooth muscle preparations were analyzed simultaneously with and under the same conditions as the corpus cavernosum. The results are as follows: The concentrations of ATP and CP in the corpora were significantly lower than the concentrations in bladder. In the corpora, the tissue concentration of CP was lower than the tissue concentration of ATP, whereas the concentration of CP in the bladder was higher than the concentration of ATP. The rate of glucose metabolism to lactic acid and to carbon dioxide was similar for both bladder smooth muscle and corpus cavernosum. The maximal enzymatic activity of the mitochondrial enzyme citrate synthase was similar for both tissues; similarly, there was no significant difference in the activity of malate dehydrogenase between the two tissues.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenine Nucleotides↗