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Biomedical subjects

F R Butcher

Publications and source records attributed to F R Butcher.

At least 55 records · Page 3Linked to original sources
PubMed1976

Effect of adenosine 3',5'-cyclic monophosphate derivatives on alpha-amylase release, protein kinase and cyclic nucleotide phosphodiesterase activity from rat parotid tissue.

Several 8-substituted derivatives of cyclic AMP were tested for their effects on alpha-amylase release. None of the 8-substituted compounds were more active than N6,O2-dibutyryl- or N6-monobutyryl adenosine 3',5'-monophosphate in causing alpha-amylase release. The rat parotid was found to contain a high (105 muM) and a low (1.15 muM) Km cyclic AMP phosphodiesterase activity. All of the 8-substituted cyclic AMP compounds inhibited the hydrolysis of 1 muM cyclic AMP. However, there was only a partial correlation between the ability to cause alpha-amylase release and inhibit cyclic AMP hydrolysis. Extracts of parotid tissue contained a cyclic AMP-dependent protein kinase activity. None of the compounds were as effective as cyclic AMP in activating the protein kinase. As in the case of inhibition of cyclic AMP hydrolysis, the ability of the 8-substituted cyclic AMP compounds to increase protein kinase activity did not correlate with their effects on alpha-amylase release. It is concluded that factors in addition to the in vitro inhibition of cyclic AMP hydrolysis and activation of protein kinase are important in determining the net result of the 8-substituted cyclic AMP compounds on parotid gland function. These additional factors might include differences in the rate of uptake and differences in rats of conversion to compounds with modified activity.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1976

Induction and decay of glucagon-induced amino acid transport in primary cultures of adult rat liver cells: paradoxical effects of cycloheximide and puromycin.

Liver parenchymal cells were isolated from adult rats and cultured in collagen-coated plastic petri dishes in serum-free medium. Glucagon induced 4- to 5-fold increases in alpha-aminoisobutyric acid (AIB) transport within 6 hr. Dexaemthasone had no direct effect on AIB transport but greatly potentiated the induction by glucagon ("permissive effect"). Levels of 3':5'-cyclic AMP increased 30- to 100-fold within 30 min after glucagon addition to cultures that had been treated with dexamethasone, and dibutyryl cyclic AMP mimicked the glucagon induction of AIB transport. Additionally, dexamethasone exerted a "permissive" effect on induction of AIB transport by dibutyryl cyclic AMP, whereas the phosphodiesterase inhibitor 3-isobutyl-1-methylxanthine induced AIB transport only in cultures that had been treated with dexamethasone. Induction of AIB transport was not dependent upon the continued presence of glucagon, but induced AIB transport activity decayed to uninduced levels within 3-4 hr after glucagon removal. The protein syntesis inhibitors puromycin and cycloheximide inhibited both induction and decay of glucagon induced AIB transport, but had a stabilizing effect if added once induction or decay had commenced. Unlike cycloheximide, the inhibitory effect of puromycin on the glucagon induction of AIB transport was reversible.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1976

Cyclic guanosine 3':5'-monophosphate and the regulation of lipolysis in rat fat cells.

The addition of the divalent cation ionophore A23187, carbachol, norepinephrine or insulin to rat fat cells elevated cyclic GMP. The increase in cyclic GMP due to these agents was greater at 4 than at 2 minutes after their addition. Cyclic GMP accumulation was also elevated by the addition of 0.1 to 0.5 mM sodium oleate in the presence of 0.1% albumin and by albumin containing added palmitate with an FFA/albumin molar ratio of 6.7. The rise in cyclic GMP due to all agents was markedly reduced in calcium-free buffer. The effects of the various agents on cyclic GMP accumulation in rat fat cells had little correlation with lipolysis. Insulin was an effective anti-lipolytic agent in both the presence and absence of calcium while neither A23187 nor carbachol had any effect on fat cell lipolysis.

Adipose Tissue↗
PubMed1975

Effect of adrenergic agents on alpha-amylase release and adenosine 3',5'-monophosphate accumulation in rat parotid tissue slices.

The role of cyclic AMP in stimulus-secretion coupling with investigated in rat parotid tissue slices in vitro. Isoproterenol and norepinephrine stimulated a rapid intracellular accumulation of cyclic AMP, which reached a maximum level of 20-30 times the control value by 5 to 10 min after addition of the drug. Isoproterenol was approximately ten times more potent in stimulating both alpha-amylase release and cyclic AMP accumulation than were norepinephrine and epinephrine, which had nearly equal effects on these two parameters. Salbutamol and phenylephrine were less effectivema parallel order of potency and sensitivity was observed for the stimulation of adenylate cyclase activity in a washed particulate fractionmthe results suggest that these drugs are acting on a parotid acinar cell through a beta1-adrenergic mechanismmat the lowest concentrations tested, each of the adrenergic agonists stimulated significant alpha-anylase release with no detectable stimulation of cyclic AMP accumulationmeven in the presence of theophylline, phenylephrine at several concentrations increased alpha-amylase release without a detectable increase in cyclic AMP levels. However, phenylephrine did stimulate adenylate cyclase. These data suggest that, under certain conditions, large increases in the intra-cellular concentration of cyclic AMP may not be necessary for stimulation of alpha-amylase release by adrenergic agonists. Also consistent with this idea was the observation that stimulation of cyclic AMP accumulation by isoproterenol was much more sensitive to inhibition by propranolol than was the stimulation of alpha-amylase release by isoproterenol. Stimulation of alpha-amylase release by phenylephrine was only partially blocked by either alpha- or beta-adrenergic blocking agents, whereas stimulation of adenylate cyclase by phenylephrine was blocked by propranolol and not by phentolaminemphenoxybenzamine and phentolamine potentiated the effects of norepinephrine and isoproterenol on both cyclic AMP accumulation and alpha-amylase release by N-6,O-2'-dibutyryl adenosine 3',5'-monophosphate; These observations may indicate a non-specific action of phenoxybenzamine, and demonstrate the need for caution in interpreting evidence obtained using alpha-adrenergic blocking agents as tools for investigation of alpha- and beta-adrenergic antagonism.

Adenylyl Cyclases↗
PubMed1975

The effects of several croton oil constituents on two types of DNA repair and cyclic nucleotide levels in mammalian cells in vitro.

The purpose of the present study was to determine the effects of two potent tumor-promoting agents on two DNA repair mechanisms and cyclic nucleotide levels in mammalian cells. Human amnion (AV3) cells were treated with low dose levels of either UV of N-acetoxy-acetylaminofluorene. Subsequently, DNA excision repair as measured by unscheduled DNA synthesis was followed in the absence or presence of non-toxic levels of either 12-O-tetradecanoylphorbol-13-acetate (TPA), phorbol-12,13-dibenzoate (PDB), both potent tumor promoters, or phorbol, a non-promoter. Neither of these compounds inhibited DNA repair synthesis occurring in response to low doses of the carcinogenic agents. In addition, TPA did not inhibit "post-replication repair" in response to UV irradiation of growing Chinese hamster (V79-4) cells. However, both TPA and PDB did cause rapid dramatic increases in cyclic guanosine monophosphate levels in human amnion cells; phorbol had no effect. Neither of these compounds affected cyclic adenosine monophosphate levels. These results are discussed in the light of a possible mechanism of the action of tumor promoters involving "post-replication repair".

Acetoxyacetylaminofluorene↗
PubMed1975

Cyclic nucleotides and gluconeogenesis by rat liver cells.

Gluconeogenesis from lactate, pyruvate, fructose, alanine, and other substrates was accelerated by glucagon or epinephrine in hepatocytes isolated from rat liver. Glucagon and epinephrine also increased cyclic AMP accumulation by rat hepatocytes. Isoproterenol increased cyclic AMP but not gluconeogenesis, while phenylephrine accelerated gluconeogenesis. The activation of gluconeogenesis by epinephrine was unaffected by propranolol but blocked by dihydroergotamine. Dibutyryl cyclic AMP added to hepatocytes stimulated gluconeogenesis at concentrations as low as 1 muM. Exogenous cyclic GMP (0.1- muM) inhibited gluconeogenesis due to either glucagon or epinephrine without affecting basal gluconeogenesis. However, carbamylcholine did not affect gluconeogenesis by hepatocytes. Basal gluconeogenesis and the increases due to all agents were inhibited by removal of extracellular calcium or the presence of A-23187, D-600, or tetracaine. In contrast, added 0.1 muM cyclic GMP, 2 mM NH-4-Cl, and 10 muM phenethylbiguanide inhibited glucagon- or epinephrine-stimulated gluconeogenesis without affecting basal values. Studies with hepatocytes indicate that the hormonal activation of gluconeogenesis is not limited to substrates entering prior to triose phosphate formation. Glucagon may act by increasing cyclic AMP which acts via unknown mechanisms to increase gluconeogenesis. In contrast, epinephrine acts via a cyclic AMP-independent mechamism which does not appear to involve cyclic GMP, Ca-2+ flux, of K+ flux.

Animals↗
PubMed1975

The role of calcium and cyclic nucleotides in alpha-amylase release from slices of rat parotid: studies with the divalent cation ionophore A-23187.

The divalent cation ionophore A-23187 caused a Ca-2+-dependent increase in alpha-amylase release from slices of rat parotid gland. The effect of A-23187 on alpha-amylase release was not caused by release of endogenous agonists since l-propranolol, phentolamine, and atropine had no effect. The magnitude of alpha-amylase release caused by A-23187 was small compared to the effect of isoproterenol. In this respect it more closely resembles the action of cholinergic and alpha-adrenergic agonists on alpha-amylase release. A-23187 inhibited the increase in the level of parotid adenosine 3,5'-monophosphate caused by isoprotrenol. The inhibitory effect required incubation of the slices with the ionophore before the addition of isoproterenol. The ionophore also caused a Ca-2+-dependent increase in the level of guanosine 3',5'-monophosphate (cyclic GMP). Theophylline enhanced the effect of A-23187 on the level of cyclic GMP. These results emphasize the role of Ca-2+ in the regulation of parotid cyclic nucleotide levels. Since the effects of the ionophore depended on the presence of Ca-2+, it is possible that some of the effects of agonists on parotid gland physiology are secondary to an action on intracellular Ca-2+ distribution.

Amylases↗