Biomedical subjects

R J Doll

Publications and source records attributed to R J Doll.

14 recordsLinked to original sources

PubMed1993

Synthesis and phosphodiesterase activity of carboxylic acid mimetics of cyclic guanosine 3',5'-monophosphate.

Synthetic analogs of the natural product griseolic acid in which a guanine base is substituted for the adenine have been prepared. The best of these compounds inhibits a cyclic guanosine 3',5'-monophosphate (cGMP) phosphodiesterase preparation with an IC50 of 0.34 microM but is a very weak inhibitor of a cyclic adenosine 3',5'-monophosphate (cAMP) phosphodiesterase. An exploration of stereochemistry indicates that the configuration of the carboxylic acids and the ring fusion in the inhibitors is important for potent cGMP PDE inhibition. PDE inhibition is not sensitive to the presence of the 2' or 4' oxygen atoms in the ribose, but inhibition is decreased when the 3' oxygen is removed. A selected group of analogs in which a monocarboxylic acid is present are poor inhibitors. The structure-activity relationship is consistent with the carboxylic acid functionality acting as a mimetic for the phosphate anion in cGMP. This concept is supported by a conformational analysis of two of the inhibitors.

3',5'-Cyclic-AMP Phosphodiesterases↗

PubMed1990

Inhibition of protein kinase C by the tyrosine kinase inhibitor erbstatin.

We examined the tyrosine kinase inhibitor erbstatin and several derivatives for their ability to inhibit serine/threonine protein kinases in vitro. Erbstatin was found to inhibit protein kinase C (PKC) with an IC50 of 19.8 +/- 3.2 microM. A trihydroxy derivative of erbstatin inhibited PKC with similar potency, whereas the corresponding methoxy derivatives were inactive. Inhibition by erbstatin was competitive with ATP (Ki = 11.0 +/- 2.3 microM) and non-competitive with the phosphate acceptor, either histone or the synthetic peptide kemptide. Action of erbstatin at the catalytic site of PKC was further indicated by the findings that it inhibited the catalytic fragment of PKC but did not inhibit the interaction of phorbol ester with the intact enzyme. Erbstatin had a similar potency against three PKC isozymes (alpha, beta, and gamma) examined. In addition, erbstatin was found to inhibit other serine/threonine kinases (assayed at their Km for ATP). The greatest potency was observed versus the cyclic nucleotide-dependent kinases, while lower potency was seen versus myosin light chain kinase. These observations are discussed in terms of the structure and kinetic properties of PKC and the epidermal growth factor receptor tyrosine kinase.

Animals↗

PubMed1988

Effect of amiloride on regulatory mechanisms of vascular smooth muscle contraction.

Experiments were conducted to characterize the effects of amiloride on the regulatory mechanisms of vascular smooth muscle contraction. Intact, saponin-skinned and A23187-treated strips of rabbit aorta were used for these studies. Amiloride significantly (P less than 0.05) reduced the norepinephrine bitartrate (NE)-stimulated increase in intracellular Ca2+ in intact arteries. In saponin-skinned arteries, amiloride depressed both stress and concomitant levels of myosin light chain phosphorylation. This inhibition of stress appeared to be competitive with MgATP. In A23187-treated preparations, where the effects of amiloride were studied at physiological [MgATP] in the absence of functional membrane Ca2+-channels, amiloride caused a reduction in both stress and myosin light chain phosphorylation. In other experiments on intact arteries, the contractile response to phorbol 12,13-dibutyrate, an activator of protein kinase C, was reduced by amiloride. We conclude that the vasorelaxant effects of amiloride are mediated via inhibition of myosin light chain kinase and protein kinase C, in addition to the inhibition of Ca2+ influx.

Adenosine Triphosphate↗

PubMed1984