Cyclic AMP Phosphodiesterase in Leydig Cell Preparations of the Rat Testis

Enzymatic digestion of the interstitial tissue of early juvenile and adult rat testes resulted in an enrichment of the Leydig cell population. The cells of the intertubular preparation from adult testes were separated by centrifugal elutriation, according to differences in sedimentation velocity, a counter-flow centrifugation technique leading to 70% Leydig cell purity. Using this approach, it was possible to demonstrate that Leydig cells from adult testes contain only low affinity isoenzymes of cyclic AMP phosphodiesterase (PDE; E.C.: 3.1.4.17), an intracellular regulator of cAMP. Starch gel electrophoresis showed that the isozyme of cAMP PDE of Leydig cells is masked in crude testis homogenates due to the relatively low level of these cells in the total population. In Leydig cells, there are two different electrophoretic forms expressed which resemble two of eleven different molecular forms of cAMP PDE demonstrated for comparison in 21 different organs of the adult rat.
An interstitial cell preparation from early juvenile testes, with a Leydig cell content of up to 20%, was also investigated electrophoretically with regard to molecular forms of cAMP PDE, the properties of which were characterized by kinetic analysis of cAMP hydrolysis. The results presented are discussed in relation to the onset of testosterone synthesis in Leydig cells of prepubertal rats leading to the initiation of male puberty.     

Recovery of Prostaglandins in Human Cutaneous Inflammation

An in-vivo skin perfusion technique has been used to study the pharmacological activity in inflamed skin of patients with allergic contact eczema. Perfusates from 35 out of 45 patients contained a smooth-muscle-contracting agent with prostaglandin-like properties. Solvent partition followed by thinlayer chromatography revealed this activity to be due to a mixture of prostaglandins E and F. This direct evidence supports the view that prostaglandins mediate inflammation in man.     

Itch: Role of Prostaglandins

Prostaglandin E₁ lowers the threshold of human skin to histamine-evoked itching. Though histamine and other mediators may produce itching by a direct action, itching in inflamed skin can also be explained by a pharmacological synergism in which low concentrations of prostaglandins, which do not themselves cause itching, potentiate itching due to histamine and possibly other agents. Alteration of threshold responses of components of inflammation to other mediators may be an important general role of prostaglandins.     

Effect of pyocyanin and 1-hydroxyphenazine on in vivo tracheal mucus velocity

Products of the bacterium Pseudomonas aeruginosa have been shown to slow the beating of human respiratory tract cilia in vitro. We have tested the effects of two of these compounds, pyocyanin and 1-hydroxyphenazine (given as a bolus dose dissolved in 2 microliters Ringer solution), on tracheal mucus velocity of radiolabeled erythrocytes in anesthetized guinea pigs. 1-Hydroxyphenazine (200 ng) caused a rapid slowing of tracheal mucus velocity (maximum fall 47% at 20 min) with recovery by 1 h. The effect of pyocyanin was slower in onset, 600 ng causing 60% reduction in tracheal mucus velocity at 3 h, and no recovery occurred. A combination of pyocyanin and 1-hydroxyphenazine produced an initial rapid slowing equivalent to the same dose of 1-hydroxyphenazine given alone, but the later slowing attributed to pyocyanin was greater than the same dose administered alone. This study demonstrates one mechanism by which products of P. aeruginosa may facilitate its colonization of the respiratory tract.