Search

Background: Lipid components are considered to play an important role in ischaemia reperfusion injury although the mechanism of their action remains unknown. Accumulation of lipid metabolites in ischaemic tissues is a consistent observation, but exactly how these lipids are cleared from the tissues by the circulating blood during reperfusion is still open to speculation. In the present study, levels of blood lipids (fatty acids, phospholipids, triglycerides, cholesterol, lysolecithin and lysolecithin platelet activating factor (lyso PAF)) and the enzyme phospholipase A2 were determined in an experimental animal model (dogs) of ischaemic reperfusion injury. Methods: The injury was induced by 4 h of aortic clamping followed by 2 h of reperfusion (unclamping). Blood samples were collected before clamping and at predetermined time intervals (0, 15, 60 and 120 min) after the release of clamp. The lipid contents were analysed and compared with sham-treated control dogs. Results: The results showed significantly elevated levels of triglycerides and phospholipase A2, during ischaemia and reperfusion in experimental animals indicating tissue damage in the ischaemic phase continuing into the reperfusion phase and the risk of systemic damage from these toxic substances. Total fatty acid content in the circulating blood showed decreasing trends during the same time interval, which suggested possible reduced clearance of accumulated fatty acids from the affected tissues. Serum cholesterol, phospholipids, lyso PAF and lysolecithin did not show any significant variation compared with control dogs. Conclusions: It is possible that the delayed clearance of fatty acids may be due to the presence of fatty acids binding proteins in the ischaemic tissue, which trap these fatty acids in the tissues during ischaemic reperfusion injury. The prolonged retention of the accumulated fatty acids in the tissues in association with elevated triglycerides and phospholipase A2 activity may contribute to ischaemia reperfusion injury.

The possible significance of low molecular weight inhibitors (Mg, citrate and pyrophosphate) in the prevention of calcium oxalate urolithiasis has been emphasized1. Estimation of total 24 h excretion of urinary inhibitors in stone-formers (SF) will not reveal any circadian fluctuations. However, measurements of 3-hourly urine samples collected over a 24 h span should give a better picture of their circadian rhythmicity, which may help to expose any urinary biological abnormalities present therein. Therefore, the circadian rhythm of the 3 h excretion of Mg, citrate and pyrophosphate, and urinary inhibitory activity towards calcium oxalate monohydrate (COM) crystallization in SF and healthy subjects (N), were investigated.

The increased excretions of lithogenic substances (calcium, oxalate and uric acid) are known to be significant risk factors in stone formation1. Twenty five stone formers (SF) and age-sex-matched healthy subjects were asked to collect 3 h urine samples over a 24 h period. These were analyzed for calcium, oxalate, and uric acid by routine procedures. Computer programs using the method of least squares were used to detect a circadian rhythm2.

Environmental factors such as diet, climate, geographical factors, and fluid intake have an important role in the etiology of urolithiasis (1). Circadian rhythmicity in the urinary volume and excretion of creatinine (Cr), oxalate (Ox), glycolic acid, phosphate (Pi), uric acid (UA), sodium, potassium, chloride, and 17-keto steroids have been reported in healthy adults. Cohorts of stone formers who belong to the same ethnic group, share the same food habits, and are exposed to similar climatic conditions may be equally susceptible to stone disease which, possibly, may be present in the form of subtle biochemical changes. The present study investigates the circadian fluctuations in stone formers and cohorts of stone formers in an endemic area in northwestern India.

Calculus formation occurs in urine supersaturated with Ca, oxalate (Ox), phosphate (Pi), and uric acid (UA) (1). The calculated degrees of supersaturation have been used to estimate risk factors for the probably formation of renal stones. Normal urine contains a variety of inhibitory substances which may prevent or retard the precipitation of these lithogenic substances in the urinary tract. These inhibitors include components like citrate, isocitrate, pyrophosphate, magnesium polyacidic peptides, and a variety of polyanionic compounds as well. The present study is concerned with the inhibitory activity (IA) and urinary excretion of lithogenic substances, and examines possible correlations between urinary UA levels and urinary inhibitory activity towards CaOx-monohydrate (COM) crystal growth.

Urinary citrate is a potent inhibitor of calcium-oxalate and calciumphosphate crystal formation. It also forms soluble complexes with calcium, thereby decreasing the calcium-specific ion activity and relative supersaturation of both calcium oxalate and calcium phosphate (1). The present investigation was performed, therefore, to study circadian variations in citrate excretion in patients suffering from calcium urolithiasis and in control subjects.