Salivary alpha amylase and salivary cortisol response to fluid consumption in exercising athletes.

The objective of the study was to examine salivary biomarker response to fluid consumption in exercising athletes. Exercise induces stress on the body and salivary alpha amylase (sAA) and salivary cortisol are useful biomarkers for activity in the sympathoadrenal medullary system and the hypothalamic pituitary adrenal axis which are involved in the stress response. Fifteen college students were given 150 ml and 500 ml of water on different days and blinded to fluid condition. The exercise protocol was identical for both fluid conditions using absolute exercise intensities ranging from moderate to high. Saliva was collected prior to exercise, post moderate and post high intensities and analyzed by Salimetrics assays. Exercise was significant for sAA with values different between pre-exercise (85 ± 10 U · ml(-1)) and high intensity (284 ± 30 U · ml(-1)) as well as between moderate intensity (204 ± 32 U · ml(-1)) and high intensity. There was no difference in sAA values between fluid conditions at either intensity. Exercise intensity and fluid condition were each significant for cortisol. Cortisol values were different between pre-exercise (0.30 ± 0.03 ug · dL(-1)) and high intensity (0.45 ± 0.05 ug · dL(-1)) as well as between moderate intensity (0.33 ± 0.04 ug · dL(-1)) and high intensity. Moderate exercise intensity cortisol was lower in the 500 ml condition (0.33 ± 0.03 ug · dL(-1)) compared with the 150 ml condition (0.38 ± 0.03 ug · dL(-1)). This altered physiological response due to fluid consumption could influence sport performance and should be considered. In addition, future sport and exercise studies should control for fluid consumption.

Risks associated with source of fiber and fiber components in cancer of the colon and rectum.

In this case-control study, we examined the food sources of fiber and fiber solubility to determine whether particular components of dietary fiber were differentially associated with risk of colon and rectal cancer. In Western New York, cases with pathologically confirmed, single, primary cancers of the colon and rectum as well as age-, sex- and neighborhood-matched controls were interviewed from 1975-1986. The sample included 428 colon case-control pairs (223 females, 205 males) and 422 rectal case-control pairs (145 females, 277 males). Subjects were interviewed regarding usual quantity and frequency of consumption of foods. For the colon, risk decreased with intake of grain fiber for both females and males and with intake of fruit/vegetable fiber for males only. Insoluble grain fiber was more strongly associated with risk than soluble grain fiber. For the rectum, fruit/vegetable fiber was associated with decreased risk, whereas grain fiber was not. There was no difference in risk for soluble and insoluble fiber components for the rectum. Analysis of risk associated with fiber by food source and by components of the fiber may provide insight into possible mechanisms of a fiber effect on cancer of the colon and rectum.

18:1 n7 fatty acids inhibit growth and decrease inositol phosphate release in HT-29 cells compared to n9 fatty acids.

Studies have shown that trans fatty acids may play a role in the development of chronic diseases such as heart disease and cancer. The objective of the present project was to examine the effect of supplementation with 18:1 isomers, both positional and geometrical, as compared to 18:0 on the growth, membrane fatty acid composition and the phosphoinositide cycle of HT-29 human colon cancer cells. Cells were supplemented with 30 microM stearic acid (18:0), elaidic acid (18:1, n9, trans), oleic acid (18:1, n9, cis), vaccenic acid (18:1, n7, cis) or trans-vaccenic acid (18:1, n7, trans) as sodium salts complexed to fatty acid-free bovine serum. Cells were grown in these media for 9 days. Cell growth was examined by counting the number of cells and expressed as percentage of control (18:0 supplemented cells). The phosphoinositide (PI) cycle was examined by measuring the inositol phosphate (IP) released from phosphoinositides in the absence (basal) or presence of stimuli (0.1 mM carbachol, 0.1 mM A23187 or 20 mM NaF). The results obtained indicated that cis and trans n7 fatty acids inhibited the growth of HT-29 cells by 11% and 23%, respectively, as compared to 18:0 supplementation. 18:1, n9 had no effect on tumor growth. Supplementation with all forms of 18:1 resulted in an increase in IP and IP2 production as compared to 18:0 supplemented cells without influencing IP3. The presence of the double bond at the 9 position in the supplemented fatty acid increases total IP production by 59% and in the cis form by 37% above the control. The breakdown of phosphoinositides in the absence and presence of several stimuli supports the observed finding on IP. Trans fatty acid supplementation resulted in lower hydrolysis of PI as compared to cis fatty acids. It is concluded that the observed inhibition of tumor growth by the vaccenic acids may be mediated by their effect(s) on the PI cycle which may be associated with their incorporation into membrane lipids.

In vitro activation and inhibition of rat colonic phospholipase D by fatty acids.

The present study was designed to examine the effect of long-chain fatty acids on phospholipase D (PLD) of the proximal colon mucosa of the rat. These fatty acids are present in the colon, in close contact with the membranes which contain the enzyme. The results indicate that unsaturated fatty acids activate the enzyme. At 4 mM, trienes are more potent activators as compared to 18:2 and 18:1. The number of double bonds and the configuration around the double bond were found to be important factors in activation of the enzyme. The metabolism of polyunsaturated fatty acids may be involved in the activation since the presence of antioxidants and cyclooxygenase inhibitors were found to influence the activation of PLD by polyunsaturated fatty acids.

Prostaglandin synthesis in human cancer cells: influence of fatty acids and butyrate.

Previous research has suggested that prostaglandins (PGs) may play a role in the development of colon cancer since tumor cells produce more PGs than normal cells. However, the exact mechanism by which PGs play a role in the development of cancer is not known. In addition, factors that influence PG synthesis are not known since they are complicated by the presence of homeostatic mechanisms. To avoid the homeostatic mechanisms, the present research was designed to examine factors that may influence PG synthesis in an in vitro system, i.e., a tissue culture. We have chosen two human colon cancer cell lines that differ in their ability to metabolize long-chain fatty acids (LCFAs), LS174T cells and HT-29 cells. We examined the effect of LCFAs on their membrane fatty acid composition, growth, and ability to release the main PGs (PGE2 and PGI). The LCFAs used were those most common in the colonic lumen [18:0, 18:2 (n-6), and 18:3 (n-3)]. In addition, we examined the effect of butyrate on the above mentioned parameters. Butyrate is produced in the colon through fermentation of dietary fibers. The data obtained suggest that although both of these tumor cell lines are of human colonic origin, they differ in their response to LCFAs and butyrate in some of the characteristics studied, such as growth, composition of membranes, and the relationship between membrane FA composition and PG synthesis. Polyunsaturated fatty acid supplementation stimulated the growth of HT-29 cells but not of LS174T cells when compared with growth in media supplemented with 18:0.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of membrane lipid alteration on the growth, phospholipase C activity and G protein of HT-29 tumor cells.

The objective of the present study was to examine the effect of modifying the fatty acid composition of membranes on cell growth and phosphoinositide specific phospholipase C (PLC) activity in HT-29 colon cancer cells. Cells were seeded at a density of 12 x 10(3) cells/cm2 and supplemented with 30 microM of either 18:0, 18:2 (n6) or 18:3 (n3) complexed to bovine serum albumin (BSA) in DMEM medium. Cell growth was followed for 12 days. The 18:0 supplemented cells (control) reached maximum growth at day nine which was greater than either 18:2 (n6) or 18:3 (n3) supplemented cells. There was no difference between the latter two groups in their growth. To investigate the fatty acid incorporation of the supplemented fatty acid and how they may influence composition in the cell membrane, we examined the fatty acid composition of each phospholipid (PL) species. Both phosphatidylcholine (PC) and phosphatidylethanolamine (PE) were significantly influenced by the type of fatty acid supplemented. Supplementation with 18:0 resulted in HT-29 cell membranes having more monounsaturated fatty acids than the cells grown in the other fatty acids. Polyunsaturated fatty acid (PUFA) supplementation (both 18:2 and 18:3) resulted in the enrichment of PUFA in the PL fractions. Cells supplemented with 18:3 (n3) had the highest unsaturation index in membrane PE as compared to the other phospholipid species. PLC activity of the membranes was measured using PIP2 as a substrate in the presence of 15 micrograms alamethicin and 42 microM free calcium. The contribution of G protein to the activity of the enzyme was assessed using GTP gamma(S). PLC activity of HT-29 cells was 16% higher in the presence of GTP gamma(S) response. GTP gamma(S)-activated PLC activity of 18:3 (n3) supplemented cells was 81% of those supplemented with either 18:0 or 18:2 (n6) cells. It is concluded that the decrease in cell proliferation with supplementation with 18:3 (n3) may be mediated through its inhibitory effect on PLC, which provides the second messengers for protein kinase C (PKC) activation. PLC may be influenced by an increased unsaturation index of the PE fraction of the HT-29 tumor cell membranes.

Influence of the level of dietary lipid intake and maximal exercise on the immune status in runners.

Chronic exercise and high fat diets are associated with immune suppression. This study compares cellular immune responses at rest and after maximal exercise in runners after eating diets comprised of 17% low fat (LF), 32% medium fat (MF), and 41% high fat (HF) (4 wk each). VO2max increased significantly from the 17% to 41% fat diet. The leukocyte cell counts were significantly increased after exercise. In men, significantly higher proliferative response to phytohemagglutinin (PHA) (P < 0.004) was observed with MF diet, while response to pokeweed mitogen (PWM) was significantly decreased by MF and HF diets. The number of CD8+ (suppressor) T cells was significantly higher in men and exercise increased it significantly, while CD4+ (helper) T cells were not affected. Natural killer cells number was significantly increased 2.5 fold by exercise and with increase in dietary fat. The production of IL-2 by peripheral blood mononuclear cells was significantly higher in men (P < 0.0001) and increasing dietary fat significantly increased IL-2 production (P < 0.001). In men, exercise decreased the level of the proinflammatory cytokines (IL-1, IL-6 and TNF-alpha), whereas in women, with the exception of MF diet for IL-6, exercise had no effect. This study indicates that short, intense bouts of exercise in runners training 40 miles.wk-1 have mixed effects on the immune system. A high percentage of fat intake (41%) did not have any deleterious effects on the immune system of the well-trained runners.

Effect of dietary fat on metabolic adjustments to maximal VO2 and endurance in runners.

The present study examined the effects of dietary manipulations on six trained runners. The percent energy contributions from carbohydrate, fat, and protein were 61/24/14, 50/38/12, and 73/15/12 for the normal (N), fat (F), and carbohydrate (C) diets, respectively. Expiratory gases and blood responses to a maximum (VO2max) and a prolonged treadmill run were determined following 7 d on each diet. Free fatty acids (FFA), triglycerides, glycerol, glucose, and lactate were measured. Dietary assessment of subjects' N diet indicated that they were consuming approximately 700 kcal.d-1 less than estimated daily expenditures. Running time to exhaustion was greatest after the F diet (91.2 +/- 9.5 min, P < 0.05) as compared with the C (75.8 +/- 7.6 min, P < 0.05) and N (69.3 +/- 7.2 min, P < 0.05) diets. VO2max was also higher on the F diet (66.4 +/- 2.7 ml.kg-1 x min-1, P < 0.05) as compared with the C (59.6 +/- 2.8 ml.kg-1 x min-1, P < 0.05) and N (63.7 +/- 2.6 ml.kg-1 x min-1, P < 0.05) diets. Plasma FFA levels were higher (P < 0.05) and glycerol levels were lower (P < 0.05) during the F diet than during the C and N diets. Other biochemical measures did not differ significantly among diets. These data suggest that increased availability of FFA, consequent to the F diet, may provide for enhanced oxidative potential as evidenced by an increase in VO2max and running time. This implies that restriction of dietary fat may be detrimental to endurance performance.

The role of dietary fat on performance, metabolism, and health.

This paper presents a model to evaluate the nutritional status of trained athletes based on work in our laboratory as well as others. The model proposes that substrate use is set by the muscle fibers recruited, based on the exercise intensity. Second, the substrate available is primarily determined by the intramuscular stores. In trained athletes, intramuscular fat plays an important role in metabolism at exercise intensities as high as 80% of maximal aerobic power. Based on these factors, increasing the fat in the diet (while maintaining adequate intramuscular glycogen) increases VO2max and intramuscular stores of fat (presumably due to increased mitochondrial volume). These two factors result in a significant increase in the time to exhaustion at set levels of exercise (endurance). It also appears that fatigue is associated with depletion of either glycogen or fat. These conclusions hold true for athletes on diets where sufficient calories are taken in to meet demands and for exercise levels below 80% of VO2max, where primarily slow-twitch oxidative fibers are used. These data may not apply in exercise where predominantly fast-twitch fibers are used. Also, these data do not apply to runners eating a hypocaloric diet, where reducing the percentage of carbohydrates may compromise their glycogen stores. It would appear that the fat in the diet can be increased to a very high level without compromising the cardiovascular or immune systems of athletes. Moreover, it can be proposed that these data could be applied to sedentary persons, as long as they are isocaloric. This would imply that the fat consumed in the diet would be used in the muscle, as in the runners, although at a lower level. Thus, the dietary intake should be matched in both total calories and percentage of fats and carbohydrates to calories consumed by daily activity. It should be cautioned that if glycogen and fat stores are compromised, protein resynthesis is inhibited and loss of muscle mass may result. This has a negative effect on the athlete's ability to perform at high levels.

In vitro [U-14C]glucose utilization by tissues of weanling rats with lateral hypothalamic area lesions one month after lesion production.

The role of the lateral hypothalamic area (LHA) in intermediary metabolism was investigated by quantitation of [U-14C]glucose oxidation to 14CO2 and 14C incorporation into the glycogen and lipid fraction of the liver, epididymal fat pad, and diaphragm. Weanling male Sprague-Dawley rats received bilateral electrolytic lesions in the LHA (LHAL rats). Sham operated rats were either fed ad libitum (CON-ADLIB) or pair-gained to the LHAL rats (CON-PG). The experiment was terminated 1 month after lesion production. LHAL rats were significantly (SIG) lighter and shorter and ate less than CON-ADLIB; LHAL rats were also SIG shorter than CON-PG, pointing to a food intake-independent lesion effect. Both LHAL and CON-PG rats had SIG less percent carcass fat than CON-ADLIB, but there was no SIG difference between LHAL and CON-PG rats. Also, LHAL rats had a SIG higher percentage of carcass protein than both CON-ADLIB and CON-PG. Furthermore, LHAL rats incorporated SIG less glucose into liver glycogen than CON-ADLIB but SIG more into CON-PG, whereas CON-PG rats incorporated SIG less into liver glycogen than CON-ADLIB, again suggesting a food intake-independent effect. There was no difference among the groups in glucose oxidation and incorporation into lipids and glycogen in both diaphragm and epididymal fat pads and liver total lipid. However, livers of CON-PG metabolized SIG more [U-14C]glucose to CO2 than did livers of CON-ADLIB, suggesting a food intake-dependent effect. There was no difference between LHAL and CON-PG rats in this parameter.(ABSTRACT TRUNCATED AT 250 WORDS)

Differential response of glucose utilization by three rat muscle tissues to dietary fatty acid composition.

Rats were fed a semisynthetic diet containing 14% of either beef fat, safflower oil, or menhaden oil plus 2% corn oil for 7 weeks, and three tissues, diaphragm, heart, and skeletal muscle, were examined for fatty acid composition in their phospholipids and triglycerides. In addition, the lipid concentrations in these tissues were examined. The in vitro oxidation and incorporation of glucose into lipids of these tissues were also examined. Skeletal muscle showed the greatest change in phospholipid composition with diet. All tissues were responsive to changes in diet in regards to the triglyceride fraction. Dietary alteration of tissue phospholipid composition did not alter lipid concentration in these tissues. However, in diaphragm tissue, rats fed the beef fat diet had lower phospholipid and higher triglyceride synthesis compared with those fed either menhaden oil or safflower oil. In addition, triglyceride synthesis was higher in the diaphragm of animals fed the menhaden oil diet as compared with the safflower oil diet. Therefore, dietary fatty acid composition may play a role in the triglyceride and phospholipid metabolism of rat diaphragm.

Primary prevention of gastrointestinal diseases.

In the belief that available information can provide reasonable guidance, we review the evidence identifying factors which increase or decrease the risk of developing several gastrointestinal diseases. In the absence of controlled studies, we review case control and other studies. As results from animal studies cannot be readily transferred to humans, we interpret them cautiously. We recommend appropriate personal behavior to reduce risk when they seem reasonably justified by the evidence.

Influence of butyrate on lipid metabolism, survival, and differentiation of colon cancer cells.

The present work was designed to study the differentiating effect of butyrate on LS174T cells after modification of their lipids with long-chain fatty acid (LCFA) supplementation. The LCFAs 18:1(n-9), 18:2(n-6), 20:4(n-6), 20:5(n-3), and 22:6(n-3) bound to added to the media of confluent cells for eight days. The fatty acid-to-albumin ratio was 3:1. The concentration of fatty acids in the media was 100 microM. On the last day, half of the flasks were treated with 2 mM butyrate. The data indicate that supplementation with polyunsaturated LCFAs having 20-22 carbon atoms resulted in a significant reduction in cell density and viability, whereas all LCFA supplementation reduced differentiation as measured by alkaline phosphatase activity. Butyrate treatment increased the density, viability, and differentiation of the tumor cells. The effect of butyrate on differentiation was mainly with cells supplemented with 18:1, 20:5, and 22:6. In the absence of LCFA supplementation, butyrate reduced the concentration of 22:5(n-6) in the cellular lipids. Also, butyrate modified the LCFAs incorporated in cells supplemented with 18:2 and 20:5, with changes occurring in 20:5(n-3), 22:5(n-3), and 22:5(n-6). Thus the present study suggests an interaction between butyrate and LCFA on differentiation and LCFA metabolism of human colon cancer cells.

Preparation of subcellular membranes from rat intestinal scrapings or isolated cells. Different Ca2+ binding, nonesterified fatty acid levels, and lipolytic activity.

Basolateral, brush-border, and Golgi-enriched subcellular membrane fractions, prepared from homogenates of rat small intestinal mucosa obtained by scraping, had unusually high concentrations of nonesterified fatty acids. These fatty acids appear to be responsible for the large amount of calcium binding, an effect that previously was shown to be reduced in vitamin D deficiency. In contrast, basolateral and Golgi membranes prepared from isolated cells had low levels of nonesterified fatty acids and calcium binding. Intermediate levels were found with isolated cells that were not put through the usual washing procedures. Addition to homogenates of scrapings of a lipase inhibitor, diethyl-p-nitrophenyl phosphate, reduced calcium binding and nonesterified fatty acids to levels similar to those in membranes prepared from isolated cells. Phospholipase A activity was low in homogenates of isolated cells and high in scrapings; this was reduced in intestinal scrapings of vitamin D-deficient rats. Ileal membranes had more calcium binding than duodenal membranes, and ileal homogenates also had greater phospholipase A activity. Preparation of subcellular membranes from rat intestinal scrapings can result in altered lipid composition, probably due to lipolytic enzyme activity; in addition to increasing cation-binding, these high levels of fatty acids may affect other membrane properties and enzyme function.

Differential effect of butyrate on lipids of human colon cancer cells.

Recently, we demonstrated that treatment of LS174T cells with 2 mM butyrate for one day had a significant effect on the composition of cellular fatty acids. In an attempt to further explore this phenomenon, we investigated the effect of long-term butyrate treatment in the presence of different fatty acids in the medium on cellular phospholipids (PLs) and triacylglycerol (TG). Cells were supplemented with 100 microM sodium salts of 18:2 (n-6), 20:4 (n-6), 20:5 (n-3), or 22:6 (n-3) as a fatty acid-free-albumin complex. The molar ratio of the albumin and these long-chain fatty acids (LCFAs) was 3:1. One-half of these cultures were supplied with 2 mM butyrate, and the pH was adjusted to 7.4. The supplementation of the LCFAs and butyrate was maintained for eight days. The present study indicates that butyrate had a differential effect on the fatty acid composition of PLs and TG of LS174T cells. This includes an increase in monounsaturates and elongation of the supplemented LCFA, and this effect was more pronounced on TG than PL fatty acids. Butyrate resulted in a significant reduction in polyunsaturated fatty acid concentration only in PLs. In general, butyrate decreased the unsaturation index (UI) of the PLs but increased that of TG. The present study also confirmed our previous observation regarding the effect of LCFAs on cellular lipids. PL and TG fatty acid chain lengths reflect those of supplemented fatty acids. The UI of these two lipid fractions increased more with supplementation of n-3 than n-6 fatty acids.(ABSTRACT TRUNCATED AT 250 WORDS)

Alteration of membrane fatty acid composition and inositol phosphate metabolism in HT-29 human colon cancer cells.

The present study was designed to investigate the role of membrane fatty acid (FA) composition on inositol phosphate (InsP) release by a human colon tumor cell line. Cells were supplemented for five days in culture with 0, 10, 30, or 100 microM sodium stearate (18:0), linoleate [18:2(omega-6)], or linolineate [18:3(omega-3)]. These FAs were supplied as a complex with FA-free bovine serum albumin. InsP release was examined in these cells with or without stimulation with deoxycholic acid (DCA) after they were labeled with [3H]myoinositol. FA enrichment was found to influence inositol incorporation into membrane lipids. Although 18:0 had no effect, 18:2(omega-6) decreased the incorporation. On the other hand, 18:3(omega-3) increased the incorporation of inositol compared with the cells supplemented with the other FAs, but they were not different from control. Basal release of total InsP was elevated only with supplementation of 10 and 30 microM 18:3(omega-3). FA supplementation with 18:0 at 30 microM and 18:2 at 30 and 100 microM resulted in downregulation of bsal release of InsP. Enrichment of HT-29 cell membranes with polyunsaturated FAs resulted in a significant increase in stimulated release of InsP, but this was not seen with saturated FA supplementation. At 10 microM supplementation, 18:2 had the greatest effect on stimulated InsP release. This effect of 18:2 disappeared at 30 microM. However, the increase in the stimulated InsP release caused by 18:3 occurred at 10 and 30 microM. DCA-stimulated release of InsP was not downregulated by any FA supplementation. This study showed that enrichment of the membranes with polyunsaturated FAs increases the response of the phosphatidylinositol cycle to DCA stimulation. In addition, enrichment with 18:3(omega-3) increases the basal turnover of InsP. It is concluded that alteration of membrane FAs has a profound effect on the phosphatidylinositol cycle.

Type of dietary fiber, not fat, alters phospholipase D and ornithine decarboxylase activities in the rat large intestine.

We investigated the effect of dietary fatty acid composition (n-6 vs. n-3) and fiber (highly fermentable vs. less fermentable) on the activities of phospholipase D (PLD) and ornithine decarboxylase (ODC) in the rat large intestine (cecum and proximal and distal colon). Twenty-four Sprague-Dawley rats (215-270 g) ate synthetic diets with 2% safflower oil plus 21.5% safflower or fish oil and 10% cellulose or guar gum for four weeks. Cecal bile acids and free fatty acids were higher in rats fed guar gum than in rats fed cellulose. Rats fed fish oil had more proximal colonic mucosal and cecal bile acids than those fed safflower oil. PLD activity was 23% lower in the proximal colon of rats fed guar gum than in those fed cellulose, but the mucosal weight was not different. ODC activity was lower but cecal mucosal wet weight was higher in the cecum of the rats fed guar gum than in the cecum of the rats fed cellulose. The activities of PLD and ODC are affected by dietary fiber and may not be accurate markers for tissue growth in the colonic mucosa.

Effect of in vitro fermentation using human faecal inoculum on the water-holding capacity of dietary fibre.

The water-holding capacities (WHC) of four sources of fibre were measured using dialysis membranes and osmotic-suction pressures of 45, 89 and 178 mosmol/1 (1, 2 and 4 atm). At all pressures, pectin had the highest WHC, followed by cabbage (Brassica oleracea) and lucerne (Medicago sativa) and then cellulose. A suction pressure of 89 mosmol/1 (2 atm) was used in the subsequent fermentation study since it had the lowest standard error of the mean and most closely approximated physiological conditions. The four fibres were anaerobically fermented in vitro with human faecal inoculum for 24 h. The WHC of the fermentation residues were measured. The potential water-holding capacity (PWHC), a function of the extent of fermentability and the WHC of the fermentation residues, was highest for lucerne, followed by cellulose, then cabbage and, finally, pectin. Only the PWHC values ranked the four fibres in the same order as in vivo values. It was concluded that the ethanol-insoluble residues containing unfermented fibre organic matter and microbial organic matter, both of which hold water, should be used to calculate PWHC and to predict the effect of fibre on rate of passage and faecal mass in humans.

Dietary fat and phospholipase A2 activity of Sprague-Dawley rat large intestine.

The present studies were conducted to examine the effect of dietary lipid content and composition [(n-6) vs. (n-3) fatty acids] on the activity of mucosal phospholipase (PL)A2 of the large intestinal tract of rats. Three segments of the large intestinal tract were examined: cecum, proximal colon and distal colon. Weanling male Sprague-Dawley rats were fed diets containing either 5% (LS) or 16% safflower (HS) or 14% menhaden oil plus 2% safflower oil (HM) for 3 wk with the oil replacing starch in the HS and HM diets on a weight basis. The lipid extracts of microsomal fractions from mucosal scrapings were examined for phospholipid and cholesterol content and fatty acid composition. Phospholipase A2 was assayed using a fluorescent substrate. Rats fed the high fat diets had lower PLA2 specific activities. The (n-3) or (n-6) fatty acid enrichment of the membranes had no effect of the activity of the enzyme. The activity of the enzyme decreased aborally from the cecum to the distal colon; the proximal colon had an intermediate specific activity.

Localization of chloride secretion in rabbit colon: inhibition by anthracene-9-carboxylic acid.

The substituted aromatic compound anthracene-9-carboxylic acid (A-9-C) was used to inhibit active Cl- secretion by the epithelium of short-circuited rabbit distal colon. Tissues were mounted in Ussing chambers and stimulated to secrete Cl- by the addition of 1 mM dibutyryl adenosine 3',5'-cyclic monophosphate to the serosal bath. Results of 36Cl-flux measurements showed that the addition of 0.1 mM A-9-C to the mucosal bath inhibited Cl- secretion by 48%. The site of Cl- secretion was determined by using conventional micro-electrodes to show that the cells of the crypt regions, and not the surface epithelial cells, responded to A-9-C by an increase in apical membrane fractional resistance from 0.75 to 0.80 and a hyperpolarization of the apical membrane from -64 to -68 mV (P less than 0.05). The sulfhydryl reagent dithiothreitol was added to the mucosal tissue bath to remove the mucus produced by goblet cells of the crypt regions of these tissues. The time for maximal inhibition of Cl- secretion by A-9-C was decreased from 30 to 15 min by removal of the mucus barrier. The effects of A-9-C on the crypt cells, as well as the effect of mucus on the inhibitory action of this compound, demonstrate that the crypt region is the site of Cl- secretion.