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K D Croft

Publications and source records attributed to K D Croft.

77 records · Page 5Linked to original sources
PubMed1984

Dissociation of effects of dietary fatty acids on blood pressure and prostanoid metabolism in Goldblatt hypertensive rats.

To study the influence of dietary modification of prostaglandin synthesis on blood pressure regulation, the effects of dietary enrichment with linoleic acid were compared with standard rat chow in three groups of 24 rats before and after renal artery constriction and contralateral nephrectomy. Dietary supplementation with 40 energy% sunflower seed oil or linseed oil respectively caused incorporation of linoleic or linolenic acids into tissue phospholipids. Relative to the sunflower seed oil, the linseed oil diet led to inhibition of prostanoid synthesis in kidney, serum or aorta in vitro and urine in vivo. Rats on both oil-rich diets had lower blood pressures than rats on a standard diet. Thus, partial suppression of prostaglandin synthesis did not accelerate one-kidney, one clip Goldblatt hypertension, nor did sunflower oil protect against hypertension in a way that could be specifically ascribed to changes in prostaglandin synthesis.

6-Ketoprostaglandin F1 alpha↗
PubMed1984

Dietary modification of platelet and renal prostaglandins.

The effects of specific types of dietary fats on prostanoid biosynthesis, platelet function and the cardiovascular system are reviewed. Studies examining the influence of dietary modification of prostanoid synthesis on blood pressure regulation in normotensive and Goldblatt hypertensive rats showed that while dietary supplementation with either sunflower or linseed oil at 40% of energy respectively stimulated and inhibited tissue prostanoids in vitro and urinary PGE2 excretion in vivo, the development of 1 kidney, 1 clip hypertension was not altered in parallel. Rats on both oil rich diets did however, show an average lower blood pressure than animals on a standard diet. In order to minimise possible non-specific effects of large amounts of dietary fats, the effects on prostanoid metabolism of different oils at 5, 20 and 40% of energy in the diet were studied. While as little as 5% dietary supplements alter fatty acid and prostanoid synthesis in platelets, it appears that higher levels (at least 20%) are required to alter significantly renal prostaglandin metabolism.

6-Ketoprostaglandin F1 alpha↗
PubMed1984

An inhibitory effect of dietary polyunsaturated fatty acids on renin secretion in the isolated perfused rat kidney.

The influence of dietary modification of polyunsaturated fatty acids (PUFA) on renin secretion, renal vascular tone and prostanoid excretion was studied in isolated perfused rat kidneys under basal conditions and in response to angiotensin II. After a four-week regimen of diets enriched with safflower oil, linseed oil or saturated fat, providing 20% of total energy intake (20 energy %), the animals which were fed linseed oil showed a significant fall in the proportion of arachidonic acid in renal phospholipids and a reduction in urinary prostaglandin excretion. In comparison with the other dietary groups, linseed oil feeding also resulted in a consistently lower renal vascular tone with increasing doses of angiotensin II. Under basal conditions both the PUFA-fed groups had significantly lower renal venous renin secretion rates relative to the saturated fat-fed control group. Infusion of angiotensin II (10 ng/min) suppressed renin secretion and abolished significant differences between the groups. As both the control group and the safflower oil group excreted similar levels of urinary prostaglandins, these results suggest that dietary enrichment with 20 energy % PUFA alters renin secretion by a prostaglandin-independent mechanism and that this may contribute to the lower blood pressures observed in these animals compared with the saturated fat-fed control group.

6-Ketoprostaglandin F1 alpha↗
PubMed1984

Dietary fat intake and blood pressure: a double blind controlled trial of changing polyunsaturated to saturated fat ratio.

The effect on blood pressure of elevating the dietary polyunsaturated/saturated fat (P/S) ratio was assessed in a double-blind, randomized control trial. Fifty-four healthy, normotensive volunteers aged between 20 and 59 years were randomly allocated either to a control group who ate a low P/S ratio diet throughout, or to one of two experimental groups who ate a high P/S ratio diet for one of two six-week experimental periods. Other nutrient changes were avoided. Twenty-four-hour diet records showed substantial changes in the P/S ratio when on the high P/S ratio diet, and no change in the control group or either experimental group when on the low P/S ratio diet. Relative concentrations of linoleic acid in plasma and cheek cell phospholipids were significantly increased when on the high P/S ratio diet. Changes in blood pressure, before and after adjustment for other possible confounding factors, were not related to changes in P/S ratio. It was concluded that an increase in P/S ratio per se cannot account for the previously reported blood pressure lowering effect of a vegetarian diet.

Adult↗