Increased collagen metabolism in granulomata induced in rats deficient in endogenous prostaglandin precursors

Collagen metabolism was measured (in terms of various hydroxyproline (HP), DNA and protein ratios) in granulomata obtained after s.c. implantation of carrageenan-impregnated and untreated polyether sponges into normal and essential fatty acid deficient (EFAD) rats for 8 and 15 days. Collagen synthesis (HP/protein) in day 8 and 15 untreated granulomata was the same for both normal and EFAD rats, though collagen breakdown (total HP) appeared to be greater in EFAD granulomata on day 15. With carrageenan-impregnated sponges, collagen synthesis in EFAD granulomata was much greater than in normal granulomata on both day 8 and day 15. Ratios of protein and/or HP to DNA (probably indicative of cellular infiltration) were increased in EFAD rats with both sponge types, though this increase was less pronounced with carrageenan-impregnated sponges. Is is suggested that endogenous prostaglandin (PG) production (markedly reduced during EFA deficiency) may exert a negative feedback effect on collagen metabolism during proliferative inflammation.     

Uteroplacental dysfunction and prostaglandin metabolism in zinc deficient pregnant rats

Relationships between perinatal mortality, disrupted uteroplacental function and prostaglandin metabolism have been studied in Zn-deficient rats. Uterine contractility $\text{in vitro}$, placental blood flow $\text{in viro}$, and uterine and placental prostaglandin synthesis from [1?¹⁴C] arachidonic acid $\text{in vitro}$ were investigated at day 22 of pregnancy. High amplitude uterine contractions were almost completely eliminated and utero-placental blood flow was decreased by 85% by Zn deficiency. Synthesis of [1?¹⁴C]-prostaglandin E₂, F_2α and 6-keto-F_1α from [1?¹⁴C] arachidonic acid decreased significantly in uterine tissue but increased in placentae. These possibly inter-related effects may contribute to the high perinatal mortality observed in Zn deficiency.     

Reduced exudation and increased tissue proliferation during chronic inflammation in rats deprived of endogenous prostaglandin precursors

Two models of chronic inflammation were studied in rats deprived of endogenous precursors of prostaglandins by feeding the animals on essential fatty acid deficient (EFAD) food. During kaolin-induced pouch-granuloma, exudate production was markedly reduced in EFAD rats, when compared with normal animals. The exudates from normal rats contained large amounts of PGE, but in the exudates from EFAD rats the amount of PGE was very markedly reduced. Similarly, with carrageenan-impregnated polyether sponges, the exudative component of inflammation was reduced in EFAD rats. However, the proliferative component was significantly increased, particularly in relation to the stunted growth of EFAD rats. Sponge exudates from EFAD rats contained fewer leucocytes than those from normal animals but the fall in leucocyte count was much smaller than the very marked reduction in PGE activity. EFAD rats also exhibited a significant increase in adrenal weights.The results are discussed in the light of the ambivalent (pro- or anti-inflammatory) role of endogenous PGs. It appears that, in the proliferative phase of inflammation, the anti-inflammatory role of PGs is more dominant.     

Cholesterol metabolism in copper deficient rats

The influence of copper deficiency on the appearance of newly synthesized cholesterol in the plasma lipids of rats was examined following ³H mevalonate injection. At 181 days copper deficient rats exhibited a highly significant increase in plasma cholesterol concentration. Copper deficiency was associated with a greatly enhanced appearance of ³H in newly synthesized cholesterol and cholesteryl esters in the plasma lipids. A concomitant decrease in ³H incorporation into liver lipids was also observed. The results suggest that copper deficiency markedly influences the clearance of hepatic cholesterol to the plasma pool, and a highly significant correlation was observed between plasma copper concentrations and ³H incorporation into plasma cholesterol. The results are discussed in terms of a possible role for copper in lipoprotein metabolism, bile acid metabolism, and the uptake of cholesterol by extra-hepatic tissues.     

Increased plasma lipidperoxidation in vitamin B-6 deficient rats

Lipidperoxidation in plasma of rats fed with vitamin B-6 deficient diet for a period of 12 weeks was studied with pair-fed controls. Plasma pyridoxal 5'-phosphate, alanine amino transferase and aspartate amino transferase, the markers of vitamin B-6 status, were significantly low in vitamin B-6 deficient rats. Plasma malondialdehyde level, conjugated dienes and lipofuscin like pigments were increased in vitamin B-6 deficiency. Increased levels of plasma lipids, calcium, iron and copper were observed in vitamin B-6 deficiency. Plasma susceptibility to lipidperoxidation was maximal in vitamin B-6 deficiency, upon stimulation by the promotors, Fe2+, Fe3+, Cu2+, ascorbate, t-butyl hydroperoxide and hydrogen peroxide.     

Carbohydrate metabolism in erythrocytes of copper deficient rats

Dietary copper deficiency is known to adversely affect the circulatory system of fructose-fed rats. Part of the problem may lie in the effect of copper deficiency on intermediary metabolism. To test this, weanling male Long-Evans rats were fed for 4 or 8 weeks on sucrose-based diets containing low or adequate copper content. Copper deficient rats had significantly lower plasma and tissue copper as well as lower plasma copper, zinc-superoxide dismutase activity. Copper deficient rats also had a significantly higher heart:body weight ratio when compared to pair-fed controls. Direct measurement of glycolysis and pentose phosphate pathway flux in erythrocytes using (13)C NMR showed no differences in carbon flux from glucose or fructose to pyruvate but a significantly higher flux through the lactate dehydrogenase locus in copper deficient rats (approximately 1.3 times, average of glucose and glucose + fructose measurements). Copper-deficient animals had significantly higher erythrocyte concentrations of glucose, fructose, glyceraldehyde 3-phosphate and NAD(+). Liver metabolite levels were also affected by copper deficiency being elevated in glycogen and fructose 1-phosphate content. The results show small changes in carbohydrate metabolism of copper deficient rats.     

Curcumin treatment modulates collagen metabolism in isoprot3erenol induced myoxardial necrosis in rats

This study was carried out to evaluate whether curcumin, a potent antioxidant, had any specific role in the synthesis and degradation of collagen in rat heart with mocardial necrosis, induced by isoproterenol.HCI (ISO). Myocardial necrosis was induced by administration of ISO (30 mg/100 g body weight subcutaneously twice at an interval of 24 h) and studies on collagen metabolism were carried out with curcumin (200 mg/kg) pre-and co-treatment with ISO. The incorporation of ₁₄C-proline into collagen was studied as an index of collagen synthesis. The heart weight /body weight ratio,heart RNA/DNA ratio and protein were found to increase significantly in ISO administered animals. Curcumin pre- and co-treatment with ISO reversed these changes and attenuated the development of cardiac hypertrophy two weeks after the second dose of ISO. Increased fractional synthesis rate and enhanced degradation of newly synthesized collagen were observed in ISO administered animals. Curcumin pre- and co-treatment with ISO was noticed to decrease the degree of degradation of the existing collagen matrix and collagen synthesis, two weeks after the second dose of ISO. The observed effects could be due to free radical scavenging capacity and inhibition of lysosomal enzyme release by curcumin.     

Increased degradation of dermal collagen in diabetic rats.

The effect of alloxan induced diabetes on the dermal collagen content of albino rats was studied in relation to few lysosomal enzymes. Diabetes decreased the dermal collagen content. The specific activities of the lysosomal enzymes studied in the diabetic rat skin were elevated. It has been established that lysosomal enzymes degrade the connective tissue components. Thus, it may be suggested that the increase in the lysosomal enzymes studied should have facilitated the decrease in dermal collagen content of diabetic rats by increasing the degradation of dermal collagen.     

Changes in pineal indoleamine metabolism in vitamin A deficient rats

Weanling, male rats were fed a vitamin A deficient (VAD) diet from 20 to 77 days of age. The circadian rhythms of the precursors and metabolites of pineal melatonin were measured along with the activity of N-acetyltransferase (NAT). Significant decreases in peak melatonin levels (0100 hours) and in nightime NAT activity (0100 and 0300 hours) were found in the pineals of the VAD rats. In contrast, the contents of serotonin, 5-hydroxytryptophan and 5-hydroxyindole acetic acid were only moderately affected by the deficiency. Daily administration of 25 micrograms melatonin from 20 to 74 days of age markedly reduced NAT activity in control and VAD rats. These data suggest that NAT activity is more sensitive to chronic VAD than any other parameters of melatonin metabolism.     

Increased lipid peroxidation in kidney of vitamin B-6 deficient rats

Lipid peroxidation in kidney of rats fed with vitamin B-6 deficient diet for a period of 12 weeks was studied with pair-fed controls. The basal lipid peroxide level as well as the degree of susceptibility to lipid peroxidation in presence of promotors such as NADPH, ascorbate, t-butyl hydroperoxide, Fe2+, Cu2+ and oxalate, were increased in vitamin B-6 deficient kidney. The observed increased lipid peroxidation in vitamin B-6 deficient kidney was correlated with high levels of lipids, copper, iron, calcium and oxalate, low levels of antioxidants and antioxidant enzymes and increased levels of hydroperoxides and hydroxyl radicals.     

Increased metabolism of bone collagen in post-menopausal female osteoporotic femoral heads

Our previous studies demonstrated that the residual collagen in osteoporotic bone was not normal but possessed higher levels of lysine hydroxylation and modified cross-linking. However, the mechanism for these changes was not clear. In the current investigation, an assessment of bone collagen metabolism in osteoporosis (OP) revealed an increase in the overall metabolism of collagen relative to age-matched controls. The increased metabolism accounts for the observed post-translational modifications of collagen which lead to a more fragile bone matrix. The rate of bone metabolism is therefore an important aspect of the pathogenesis of osteoporosis, the greater the turnover the greater the propensity of a more fragile tissue. Clearly, the quality of bone tissue does not depend solely on adequate bone density but also on the state of the collagenous matrix.     

Benzo(a) pyrene metabolism in vitamin A deficient rats

Hepatic microsomal metabolism of benzo(a)pyrene, a representative carcinogenic polycyclic hydrocarbon and an ubiquitous environmental pollutant was studied in control and vitamin A deprived (10–12 weeks) male rats. Hydroxylation of benzo(a)pyrene to fluorescent phenols was found to be significantly depressed in the deficient animals. The decreased hepatic metabolism may lead to delayed clearance of the carcinogenic chemicals in this condition and thus may explain at least in part the enhanced susceptibility to carcinogenesis in hypovitaminosis A.     

Increased muricide and decreased avoidance and discrimination learning in thiamine deficient rats.

This study assessed the effects of diet-induced thiamine deficiency in rats on two aspects of behavior, aggression and learning. Evidence of enhanced aggression (increased mouse killing) was noted with severe thiamine deficiency, but before the onset of overt neurological signs of thiamine deprivation. This behavioral change was rapidly reversible with thiamine. A similar degree of thiamine deficiency failed to alter learning of two-way shuttle-box avoidance acquisition. Animals with a gross neurological deficit did exhibit a major impairment in shuttle-box performance, but this was probably due to ataxia. However, when such rats were administered thiamine with total reversal of the neurological signs, testing in a three chambered Y-maze avoidance-discrimination apparatus also revealed impaired learning of both responses. These data demonstrate the presence of enhanced aggression during thiamine deprivation and of a persistent learning impairment in rats following reversal of this vitamin deficiency.     

Tyrosine sulfation in precursors of collagen V

Radioactive labeling of p-collagens V, collagens V, and, to a small extent, of procollagen V occurred when [35S]sulfate was incubated with tendons or primary tendon cell cultures, or blood vessels and crops of 17- to 19-day-old chick embryos, or with lung slices from neonatal rats. Most or all of this label is in the form of 1 or more sulfated tyrosine residues/chain of p alpha 1(V), alpha 1(V), p alpha 1'(V), alpha 1'(V), p alpha 2(V), and alpha 2(V), and it remains attached through purification by dialysis, ammonium sulfate precipitation, CsCl-GdnCl2 equilibrium buoyant density and velocity sedimentations, ion-exchange chromatography, and sodium dodecyl sulfate gel electrophoresis. Radioactive tyrosine sulfate was identified in alkaline hydrolysates of these collagen V chains, after labeling the tissues with either [35S]sulfate or [3H]tyrosine, by electrophoretic and chromatographic comigration with a tyrosine sulfate standard. Tunicamycin A1, which inhibits the attachment of N-linked complex carbohydrate, did not interfere with the sulfation process. The tyrosine sulfate is located in a noncollagenous domain, which is probably adjacent to the amino end of the collagen helix, and is retained throughout the physiological proteolytic processing of procollagens V. After digestion with Staphylococcus aureus V8 protease, 35S-labeled p alpha 1(V) and alpha 1(V) chains gave the same map of labeled peptides, and this differed from the map given by p alpha 1'(V) and alpha 1'(V) chains. Little sulfation of p alpha 2(V) and alpha 2(V) chains occurs. The implications of these observations for the structure and properties of procollagens V and their derivatives are considered.     

Experimental hyperthyroidism in rats suppresses in vitro prostaglandin metabolism in lung and kidney

Metabolism of prostaglandin (PG) F2α and PGE2 was depressed 40–62% in 100,000 g cytoplasmic supernatants of lungs and kidneys prepared from rats made hyperthyroid by 18 daily L(-) thyroxine injections (200μg,s-c). These hyperthyroid rats had elevated serum thyroxine levels, cardiac hypertrophy and thyroid atrophy. There were no differences in soluble protein concentrations, NAD⁺ utilisation by endogenous enzymes and substrates, or in the NAD⁺ dependence of 15-hydroxyprostaglandin dehydrogenase (15-PGDH) between the supernatants prepared from hyperthyroid rats and saline-injected controls. Thyroxine did not inhibit PG metabolism in vitro up to 260 μM. These results suggest that thyroxine specifically decreases intracellular levels of PG-metabolising enzymes, especially of the rate-limiting 15-PGDH. Metabolism of PGF2α and PGE2 by 15-PGDH was faster in smaller rats and declined with increasing animal weight. These studies imply that some of the clinical features of hyperthyroidism in man might be caused by deficiencies in PG metabolism.