[37] Preparation and characterization of a hormone antagonist from adipocytes

Ho, Ren-Jye; Bomboy, James D.; Wasner, H.K.; Sutherland, Earl W.

doi:10.1016/s0076-6879(75)37039-0

Cited by 35 publications

(37 citation statements)

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“…In this study, we have devised a new but simple perifusion technique, designed to minimize the known inhibitory effect of free fatty acids on adipose tissue lipolysis (4,5,23,28). We have employed this,technique to examine the activity of HSL in whole human adipose tissue and in the adipose cells isolated from the tissue.…”

Section: Speculationmentioning

confidence: 99%

Hormone-Sensitive Lipase in Human Adipose Tissue, Isolated Adipocytes, and Cultured Adipocytes

1982

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SummaryEmploying a perifusion technique, the activity of hormone-sensitive lipase (HSL) in human adipose tissue and isolated adipocytes was found to be significantly stimulated by 5 p M epinephrine (5-fold, P < 0.001) or 0.5 mM theophylline (2-fold, P < 0.03). The stimulatory effect of both, however, was not cumulative; instead, theophylline appeared to blunt the epinephrine effect. The two effectors together produced a 3-fold increase in activity over basal ( P < 0.01). Basal lipolysis was highly and significantly correlated with epinephrine and/or theophylline stimulated lipolysis in the tissue as well as in the isolated cells.The activity of the enzyme was examined in cultured human adipocytes using a cell-free system. The basal activity of H S L in the 20,000 x g supernatant (Szo) fraction of cultured cells grown in fat-enriched medium was significantly higher than the value in the same fraction of cells grown in regular medium (6.06 + 1.49 versus 2.78 + 0.89 nmole glycerol/min/mg protein, mean + S.D., P < 0.01), and was similar in the Szo fractions of cells grown in the enriched medium and the original tissue (6.06 + 1.49 versus 5.44 + 2.73 nmole glycerol/min/mg protein, mean + S.D., P > 0.83).When the tissue and cells were stimulated in vitro before fractionation, the H S L activity in the ,' & fraction of the original tissue increased 4-fold over basal (P < 0.001), whereas that in the cultured cells increased 2-fold ( P < 0.01) regardless of the culture medium employed. In the S z o fractions derived from basally incubated samples, but not in those derived from the epinephrinestimulated samples, the H S L enzyme was slightly but significantly ( P < 0.002) activated by exogenous addition of ATP, cyclic AMP, and protein kinase.The data suggest that the activity of HSL is retained in cultured human adipocytes and could be enhanced under conditions of culture which favor lipid accumulation and adipose conversion. SpeculationAlthough the hormone-sensitive lipase enzyme protein in adipose tissue of the rat and the chicken has been extensively purified, the human enzyme remains difficult to purify. The finding in this study, that human adipose tissue hormone-sensitive lipase activity is retained in culture, should facilitate the purification and characterization of the enzyme in man, promote the study of the cellular mechnisms involved in the synthesis, transport and degradation of the enzyme and enhance the search for possible genetic heterogeneity of the enzyme among individuals suspected to have genetic obesity.The enzymes involved in lipid metabolism in adipose tissue have been extensively studied (22,29,30,33,38,39,40,46,49); however, the so-called hormone sensitive lipase (HSL) has proved difficult to obtain in sufficiently high purity for characterization. In the crude preparation, it appears tightly bound to large lipidrich particles from which it is difficult to separate (34). Recently, it has become possible to extensively purify and characterize the enzyme in the adipose tissue of the rats and the chi...

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Section: Speculationmentioning

confidence: 99%

Hormone-Sensitive Lipase in Human Adipose Tissue, Isolated Adipocytes, and Cultured Adipocytes

1982

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“…Such a mechanism has been demonstrated in adipocytes where there is a progressive decrease in the stimulation of adenylate cyclase by adrenaline, adrenocorticotrophin or glucagon where this has been shown as being due to the release by these materials of an inhibitor (Ho & Sutherland, 1971). Another hypothesis, based on Paton's proposed mechanism of drug receptor interaction (Paton, 1961), is that tachyphylaxis results from saturation of tissue receptors such that they 802 SOMATOSTATIN AND H+ TACH YPHYLAXIS become progressively less sensitive to subsequently administered stimuli (Page & Bumpus, 1961 Coy, Coy, Arimura & Schally (1973).…”

Section: Introductionmentioning

confidence: 98%

The effects of somatostatin and metiamide on tachyphylaxis of pentagastrin stimulated gastric acid and pepsin secretion in the conscious cat.

Albinus¹,

Blair²,

Hirst³

et al. 1977

The Journal of Physiology

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3. The inhibition of pentagastrin stimulated acid and pepsin secretion by Somatostatin delays the tachyphylaxis of these responses, but the rates of tachyphylaxis when they do subsequently occur are identical.4. Metiamide 1O mg. kg-'. hr-' equally inhibits histamine and pentagastrin stimulated acid secretion but does not inhibit pentagastrin stimulated pepsin secretion.5. Inhibition of acid secretion during metiamide infusion neither prevents nor delays acid nor pepsin tachyphylaxis.6. It is suggested that tachyphylaxis of acid and pepsin secretion is a gastrin receptor phenomenon and that Somatostatin occupies or modifies the behaviour of these receptors, preventing tachyphylaxis. Metiamide, however, exerts its action only on the histamine H2-receptor and not the gastrin receptor mechanism, and this apparently does not prevent or delay acid tachyphylaxis.

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“…Ho and SUTHERLAND(1971)and others (MANGANIELLO et al,1971),using isolated fat cells,suggested that the formation of the soluble inhibitor of adenylate cyclase takes place as a result of hormonal stimulation,and that the inhibitor, in turn,inhibits hormone-induced cyclic AMP formation.We,however,could not detect any inhibitory activities in the medium obtained by incubating the slices with norepinephrine.Our results indicate that refractoriness is not due to the formation of the soluble inhibitor.It has also been reported (Ho and SUTHER-LAND,1971)that in adipocyte the formation of the soluble inhibitor is stimulated by both cyclic AMP and dibutyryl cyclic AMP.Thus,our observations of sistent with the interpretation that the refractoriness is not mediated by the formation of the soluble inhibitor.It has been reported that epinephrine increased the release of the hormone antagonist from the isolated fat cells but not from the tissue fragments (SCHIMMEL,1974).Consequently,there remains some possibility that the inhibitor produced by the parotid slices,which accumulates within the tissue but does not diffuse out,exerts its effect intracellularly. BATZRI and SELINGER(1973)have reported that the addition of norepinephrine markedly decreased the ATP content of parotid slices their reports may suggest the possibility that refractoriness may be caused by a decrease in ATP content.…”

Section: Discussionmentioning

confidence: 99%

Refractoriness of the Cyclic AMP Response to Catecholamines in Rat Parotid Slices In Vitro

1980

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[37] Preparation and characterization of a hormone antagonist from adipocytes

Cited by 35 publications

References 8 publications

Hormone-Sensitive Lipase in Human Adipose Tissue, Isolated Adipocytes, and Cultured Adipocytes

Hormone-Sensitive Lipase in Human Adipose Tissue, Isolated Adipocytes, and Cultured Adipocytes

The effects of somatostatin and metiamide on tachyphylaxis of pentagastrin stimulated gastric acid and pepsin secretion in the conscious cat.

Refractoriness of the Cyclic AMP Response to Catecholamines in Rat Parotid Slices In Vitro

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