Adipose Tissue Of Hamsters Research Articles

The synthesis of higher glycerides via the monoglyceride pathway in hamster adipose tissue

The monoglyceride pathway for the synthesis of triglycerides has been investigated employing subcellular fractions and whole cell preparations of white and brown adipose tissue. Conclusive evidence has been obtained for the monoglyceride pathway in these tissues by employing the 2-monoether analogue of 2-monoolein as the substrate. The monoglyceride and alpha-glycerophosphate pathways were primarily found in the microsomal fraction. In these in vitro systems the activity of the monoglyceride pathway compared with the alpha-glycerophosphate pathway was of the same order of magnitude in whole cell preparations and was approximately one-half the activity of the alpha-glycerophosphate pathway when the microsomal fraction was employed.

Lipolytic activity of synthetic porcine secretin.

Synthetic porcine secretin is a potent lipolytic agent on the adipose tissue of the rat and on the free fat cells of the mouse. The minimal effective dose is 0.1 μg/ml for the rat epididymal adipose tissue slice and 0.001 μg/ml for the free fat cells (mesenteric + perirenal) of the mouse. Secretin has no lipolytic effect on the adipose tissue of hamster, guinea pig, rabbit or pigeon. Bovine glucagon, which is similar in structure to porcine secretin, is active on adipose tissue or free fat cells of rat, mouse, guinea pig and pigeon, and inactive on adipose tissue of hamster and rabbit. (Endocrinology 85: 214, 1969)

Comparison of the responsiveness of perirenal adipose tissue of the rat, hamster, guinea pig and rabbit to the antilipolytic action of insulin.

Previous studies in several laboratories have demonstrated marked species differences in the hormonal responsiveness of mammalian adipose tissue. The present investigation extends these comparative studies by comparing the antilipolytic potency of insulin upon the perirenal adipose tissue of rat, hamster, guinea pig and rabbit. Epididymal adipose tissue of the rat was also studied. Lipolysis was stimulated in vitro in slices of adipose tissue from these 4 species by incubation with 1 μg/ml epinephrine, adrenocorticotropin (ACTH) or β-melanocyte-stimulating hormone (β-MSH) in albumin-free, glucosefree Krebs-Ringer phosphate medium; the lipolytic response to these hormones, in the absence and presence of 0.00001-10 μg/ml insulin, was determined by measuring the free fatty acid (FFA) concentration in the tissue slices after a 2-hr incubation. Bovine insulin at a concentration of 0.0001-.001 μg/ml or greater inhibited the lipolytic response of rat adipose tissue to epinephrine or ACTH by 50-95 %. At a concent...

INACTIVATION OF INSULIN BY ADIPOSE TISSUE.

A previous investigation in this laboratory demonstrated that rat adipose tissue contains an insoluble peptidase system which cleaves and inactivates adipokinetic hypophyseal peptides; adipose tissues from the rabbit and guinea pig possess little or no capacity to inactivate these peptides. The present study demonstrates that adipose tissues from the rat or hamster, but not from the rabbit or guinea pig, cleave and inactivate insulin. Incubation of bovine insulin with homogenized adipose tissue from the rat causes cleavage of the peptide into at least seven fragments and disappearance of the peptide's hypoglycemic activity. Unlike native insulin, the insulin fragments which contain tyrosine are soluble in 5 per cent trichloracetic acid. The insulin-inactivating system is located in the insoluble portion of homogenized adipose tissue. Inactivation of insulin does not proceed at a detectable rate at 0° C. The capacity of the insoluble fraction of rat adipose tissue homogenate to cleave and inactivate insulin is abolished by exposure to 100° C. for two minutes. An insulin-inactivating system with the same properties is found in lesser amount in hamster adipose tissue. It is not present in detectable amount in the adipose tissue of the rabbit or guinea pig. The adipose enzyme system which inactivates insulin resembles the system which inactivates hypophyseal peptides in regard to the characteristics described above.

INACTIVATION OF THE ADIPOKINETIC PROPERTY OF ADRENOCORTICOTROPIN, BETA-MELANOCYTE-STIMULATING HORMONE, VASOPRESSIN AND PITUITARY FRACTION H BY TISSUES OF THE RAT AND RABBIT.

This report presents data on the rates of inactivation of 4 adipokinetic hypophysial peptides by adipose and extraadipose tissues of the rat and rabbit, and correlates these data with the in vitro and in vivo adipokinetic potencies of the peptides in these 2 species. The peptides under study (adrenocorticotropin, β-melanocyte-stimulating hormone, vasopressin and pituitary fraction H) were incubated for 1 hr with various tissue homogenates, and the adipokinetic activity remaining in the incubation mixture was then determined by introducing slices of rabbit, guinea pig, hamster or rat adipose tissue. The data showed: 1) Eight tissues of the rat (kidney, liver, adrenal, adipose tissue, lung, heart, testis and spleen) inactivate one or more of the peptides. 2) Ratios of the rates of inactivation of the 4 peptides vary markedly from one organ to another, and indicate the presence of at least 3 different inactivating enzymes in the rat. 3) While rat adipose tissue inactivates all 4 peptides under study, rabbit ...

Dose-response curves for the adipokinetic action of aromatic amines and adrenocorticotropin upon the isolated adipose tissue of the hamster

Slices of hamster adipose tissue were incubated with various concentrations of an aromatic amine or of adrenocorticotropin (ACTH). The curve relating response (measured in terms of FFA produced) to logarithm of dose was sigmoid for all adipokinetic substances tested. The basic requirement for adipokinetic activity was found to be a phenyl group attached to an ethyl- or propylamine side chain. Structural features incompatible with adipokinetic activity are described. Three groups of sigmoid log dose-response curves were distinguished, characteristic of (a) ACTH, and the catechol amines norepinephrine, epinephrine, isoproterenol, ethylnorepinephrine, and 3,4-dihydroxy-α(isopropylamino)-acetophenone; (b) dichloroisoproterenol; and (c) nine aromatic amines related in structure to phenylethylamine, but lacking the combination of a catechol ring and a hydroxy or keto group on the Β-carbon. A modification of the Clark-Stetten model of hormone action is presented. Dose-response data for the action of aromatic amines and of ACTH upon hamster adipose tissue, and for the action of ACTH upon rabbit adipose tissue, are compatible with the equations derived from the model. Consideration of the structural features of aromatic amines, which influence certain parameters of these equations, supports the concept that the various adipokinetic peptides and the catecholamines act at the same site and by the same mechanism to stimulate lipolysis within the fat cell.