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PubMed2005

Lipid metabolism during lactation: a review of adipose tissue-liver interactions and the development of fatty liver.

Fatty acids are the major source of energy for most tissues during periods of negative energy balance; however, fatty acids can, in some circumstances, have pathological effects. Fatty acids are stored as triacylglycerols (TAG), mostly in the various adipose tissue depots of the body. However, if blood unesterified fatty acid (NEFA) levels are elevated for prolonged periods, as may occur during lactation or obesity, TAG can accumulate in other tissues including liver and muscle cells (myocytes), and this can have pathological consequences such as the development of ketosis (Grummer, 1993; Drackley et al. 2001) or type 2 diabetes (Boden & Shulman, 2002; McGarry, 2002).

Adipose Tissue↗
PubMed1993

[Follow-up of tissue acidosis, lactic acid production and morphologic changes in testicular tissue in ischemia and the effect of cooling].

More than 90% of the patients with a testicular torsion are loosing their testis by orchiectomy or by following ischemic atrophy. The critical time of irreversible changes of the testis is according to literature 4-6 hours. The aim of our study was to measure the tissue acidification (pH) in the testis at different temperatures and to estimate the cooling effect on pH, lactate accumulation and morphological changes. We have measured in 36 human testis (orchiectomy in patients with metastatic prostate cancer) the tissue acidification (pH), the tissue lactate level and the morphology changes at a temperature of 35, 25, 15 and 5 C. In 12 testis of young dogs we have measured the same parameters. Starting with a normal testis temperature of 35 C the pH is falling to 6.0 within 1 hour of ischemia. By colling to 15 C this time can be prolonged to 6 hours. The tissue lactate level rises from 25 mumol/gdw to nearly 200 mumol/gdw at 35 C. The morphology of semi-thick slices of the testis shows a swelling of the intratubular tissue (spermatogenesis) by loss of the interstitial space. By reducing temperature also a slowdown of the changes can be observed. The critical pH value of the testis for irreversible changes is not known. A ph of less than 6.0 is probably a value, which may result in such changes.

Acid-Base Equilibrium↗
PubMed1995

Transforming growth factor-alpha promotes mammary tumorigenesis through selective survival and growth of secretory epithelial cells.

Transforming growth factor (TGF)-alpha stimulates the growth and development of mammary epithelial cells and is implicated in the pathogenesis of human breast cancer. In this report we evaluate the consequences of overexpressing TGF-alpha in the mammary gland of transgenic mice and examine associated cellular mechanisms. When operating on a FVB/N genetic background (line MT100), TGF-alpha induced the stochastic development of mammary adenomas and adenocarcinomas f secretory epithelial origin in 64% of multiparous females. In contrast, tumors were exceedingly rare in virgin MT100 females, MT100 males, and multiparous FVB/N females. In MT100 females multiple foci of hyperplastic secretory lesions preceded the development of frank tumors; these initial lesions appeared during the involution period after the first lactation. Serial transplantation of these hyperplasias indicated an absence of proliferative immortality. Nevertheless, they gave rise to tumors at a low frequency and after a prolonged latency in virgin hosts; in multiparous hosts, tumors developed earlier and at a high incidence. The TGF-alpha transgene was highly expressed in hyperplasias and tumors but not in virgin and nonlesion-bearing tissue, suggesting that TGF-alpha overexpression provides a selective growth advantage. TGF-alpha also induced at lactation a 6.4-fold increase in DNA synthesis in MT100 epithelial cells, many of which were binucleated. MT100 mammary tissue experienced an obvious delay in involution, resulting in the postlactational survival of a significant population of unregressed secretory epithelial cells. In contrast, another line of transgenic mice on a CD-1 genetic background (MT42), in which TGF-alpha overexpression induced liver but not mammary tumors, failed to demonstrate postlactational epithelial cell survival. These data show that TGF-alpha promotes mammary tumorigenesis in multiparous MT100 mice by stimulating secretory epithelial cell proliferation during lactation and prolonging survival during involution. These points support the notion that TGF-alpha can act as a mitogen and also as a differentiation factor in mammary epithelium.

Adenocarcinoma↗
PubMed2001

Thyroid hormone excess and glucose intolerance.

The elevated plasma glucose levels in hyperthyroidism may be explained by increased rates of endogenous glucose production, due mainly to increased gluconeogenesis. The rates of insulin-stimulated glucose disposal in peripheral tissues in hyperthyroidism have been found, in general, either normal or increased. Skeletal muscle is the most important tissue for the disposal of glucose in response to insulin. In this tissue, insulin increases glucose disposal by stimulating glucose transport, glucose phosphorylation/glycolysis, glycogen synthesis and glucose oxidation. Studies examining insulin-stimulated glucose metabolism in skeletal muscle have suggested that, in the hyperthyroid state, it may be of primary importance to increase the rates of glycolysis and lactate formation relative to glucose oxidation in this tissue in order to provide substrate for gluconeogenesis (increase Cori cycle activity). This effect will be achieved primarily by a decrease in glycogen synthesis and an increase in glycogenolysis. When hyperthyroidism becomes more severe, an increased rate of glucose uptake into muscle may then be necessary since the increased conversion of glycogen to lactate could not be sustained for prolonged periods and might lead to a depletion in glycogen stores. This mechanism would ensure that the level of glucose in plasma is kept normal or slightly increased. Thus, an increased Cori cycle activity may be a necessary mechanism to provide optimal conditions in hyperthyroidism for the control of glucose utilization without increasing the risk of hypoglycemia. In addition to lactate, increased rates of gluconeogenesis in hyperthyroidism can also be sustained by increased plasma concentrations of amino acids (mostly glutamine and alanine) and glycerol, as well as by increased plasma concentrations of free fatty acids.

Animals↗
PubMed1992

Does anaerobic threshold correlate with maximal lactate steady-state?

The aim of this study was to compare the 'anaerobic threshold' (AnT) of subjects determined during a continuous 2-min incremental exercise test until exhaustion and the 'maximal lactate steady-state' (BLaSsmax) determined during prolonged exercise at constant loads corresponding to the subjects' AnT and/or 5-25% above and below it. Seventeen subjects performed an incremental exercise test and 1-5 prolonged exercise tests on a cycle ergometer until exhaustion at intervals of 1 week, and work rates, oxygen uptake (VO2) values and brachial venous blood lactate (BLa) levels were measured. It was proposed that when exercising at a constant workload below AnT, BLa would fall after having reached its peak; at the level of AnT, BLa reaches maximal steady-state (BLaSsmax); and above AnT, BLa increases continuously. Altogether, in 34 of 45 tests with a constant workload between 80 and 125% AnT, BLa values were as expected. In those cases in which BLaSsmax was reached, BLa increased on average by 3.8 mM from resting levels. This increase was 2.0 mM greater than that seen between resting levels and AnT during incremental exercise. There was no correlation between BLa values at BLaSsmax and at AnT, both when expressed as an increase in BLa (delta BLa) and absolute BLa concentration. Altogether, 81% of the variation in BLa concentration at BLaSsmax could be explained by the subjects' age, the percentage of slow-twitch fibres and BLa levels at rest. The AnT and BLaSsmax did not differ significantly, and these values were correlated (r = 0.83). Together, AnT and age accounted for 85% of the variation seen in BLaSsmax. The BLaSsmax did not correlate with AnT when fixed at a BLa concentration of 4 mM (AnT4mM). The three hypotheses tested in this study were confirmed, and the present results demonstrate that AnT correlates with BLaSsmax. The few exceptions to anticipated BLa kinetics were small in magnitude and could be explained by physiological variations.

Adenosine Triphosphatases↗
PubMed1977

Rat mammary deoxyribonucleic acid synthesis during the estrous cycle, pregnancy, and lactation in relation to mammary tumorigenesis: its implication for human breast cancer.

Rat mammary DNA synthesis is greatly reduced during late pregnancy and lactation; this corresponds to the decreased incidence of induced mammary tumors by chemical carcinogens during these periods. The protective effects of pregnancy and lactation against mammary tumorigenesis of rats and human subjects may be explained by the prolonged phases of mitotic rest encountered during pregnancy and lactation.

Animals↗
PubMed1990

Udder health implications of premature bovine mammary regression. I. Clinical, subclinical and reducing-sugar changes in milk during 168 hours of suspended milking in mid-lactation.

The investigation involved 4 mastitis-free cows, exposed to 168 h of suspended milking to induce prolonged milk stasis and premature mammary regression during mid-lactation. After 48 h the milk stasis elicited mastitis-like changes in the clinical, somatic cell count (SCC), bovine serum albumin (BSA) and beta-N-acetyl-D-glucosaminidase (NAG) characteristics of the udder secretions. Such changes in secretions from non-mastitic regressive mammary glands raise doubts about the present knowledge, definition, and diagnosis of so-called non-specific or aseptic mastitis. Determinations of fluctuating lacteal concentrations of lactose, galactose, mannose and glucose suggest that the secretory epithelium altered its metabolism and integrity in response to the intramammary perturbation by following a certain pattern of regressive adjustments which: (i) were apparently triggered during the initial 24 h of perturbation by disturbed Na-K-ATPase activities, followed by a cascade of changes in ion regulation, carbohydrate metabolism and increased formation of lactic acid as a metabolic end-product; (ii) advanced in a stepwise fashion during 0-24, 24-72 and 72-168 h of perturbation from recognition response to alarm reactions and manifestation of regression respectively; (iii) showed that markedly decreased carbohydrate levels preceded major increases of the SCC, BSA and NAG values; (iv) indicated that after 72 h of milk stasis leucocytic infiltrations sharply increased the SCC to more than 500,000 per ml and accelerated the manifestation of regression. The results of this study imply that extensive premature regression of healthy, and especially, pre-irritated udders could have significant implications for the development of different types of bovine mastitis during lactation and should be further investigated.

Animals↗
PubMed1995

Anti-progesterone effects on maternal recognition and behaviour imprinted during first pregnancy in mice.

Anti-progesterone treatment using specific anti-progesterone antibodies or a progesterone receptor (PR) antagonist during first pregnancy impairs postpartum maternal behaviour in mice. This effect is demonstrable only if the treatment is given during pregnancy but not immediately after parturition. The purpose of the present studies was to investigate if maternal behaviour is also impaired by anti-progesterone treatment in subsequent pregnancies. Studies with a monoclonal antibody to progesterone (DB3; 4.5 nmol/mouse) showed that injection of females on day 17 of second pregnancy did not cause maternal rejection but the latency of pup retrieval was prolonged especially during the first 3 days of lactation. This phenomenon was not observed in animals that had previous experience of full length lactation. Experiments were carried out with mifepristone (RU486; 10 micrograms/mouse) injected at day 17 of first, second or third pregnancies. Pup rejection (22.5% vs 12.3%) and prolongation of the retrieval latency (62.3 +/- 13.3 vs 19.7 +/- 6.5 s; P < 0.02) were observed following the first pregnancy. No abnormal behavioural effects were found in mothers treated in second or third pregnancy who had prior full length lactation experience. Control females subjected to only one pup retrieval test after first delivery rejected their pups if treated in their second pregnancy (27.3% vs 4.4%; P < 0.001) and displayed a marginal prolongation of the retrieval latency period (20.9 +/- 7.0 vs 7.4 +/- 2.6 s). Anti-progesterone treatment had no negative influence when administered during third pregnancy.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1988

Insulin, dexamethasone and their interactions in the control of glucose metabolism in adipose tissue from lactating and nonlactating sheep.

1. Lactation results in decreased glucose and acetate utilization and increased lactate output by sheep adipose tissue. 2. The ability of insulin to stimulate acetate uptake was lost in adipose tissue from lactating sheep, whereas both the response and the sensitivity (ED50) for insulin for stimulation of glucose conversion into products other than lactate were decreased. These impairments were partly restored by prolonged incubation of adipose tissue for 48 h. 3. The ability of insulin to stimulate lactate output was not altered by lactation. 4. Dexamethasone inhibited glucose uptake, lactate output and glycerol output in adipose tissue from both non-lactating and lactating sheep, with an ED50 of about 1 nM. Dexamethasone inhibited acetate uptake by adipose tissue from non-lactating sheep, but this effect was not observed with adipose tissue from lactating sheep. 5. Dexamethasone inhibited the stimulation of glucose uptake at all concentrations of insulin used; the effect varied with insulin concentration and resulted in an accentuation of the insulin dose-response curve. The insulin dose-response curve in the presence of dexamethasone was muted during lactation. 6. The overall effect of these adaptations is to ensure that glucose and acetate utilization by adipose tissue after an insulin surge is diminished during lactation.

Adipose Tissue↗
PubMed2006

Respiratory physiology of the Oniscidea: aerobic capacity and the significance of pleopodal lungs.

The radiation of the terrestrial isopods (sub-order Oniscidea) has been accompanied by evolution of pleopodal lungs in the sections Tylida and Crinocheta. To understand the significance of such lungs for aerobic respiration, comparative studies were conducted using 6 species. Ligia occidentalis, lacking lungs, behaved as a metabolic conformer in reduced PO(2), and showed decreased V(.-)O(2) in low humidity and following dehydration. In species possessing lungs, metabolism was insensitive to dehydration. However, lung development did not show a clear relationship to metabolic regulation: Porcellio dilatatus was a metabolic conformer while Tylos punctatus and Armadillidium vulgare were efficient regulators. The metabolic conformers did not accumulate lactate during moderate hypoxia (10% O(2)), indicating that reduced V(.-)O(2) is not compensated with anaerobic glycolysis. In contrast, Alloniscus perconvexus, a littoral species with limited metabolic regulation, showed the largest lactate accumulation during hypoxia and also possessed the highest tissue LDH activity. It is hypothesized that these are adaptations to periodic hypoxia in sand burrows and the high metabolic cost of burrowing. Differences in lactate accumulation during immersion were curious, with the largest increases occurring in L. occidentalis and A. perconvexus that tolerate prolonged immersion in seawater. Possible functions of this lactate accumulation may include modulation of hemocyanin oxygen affinity.

Anaerobiosis↗
PubMed1988

[Chemical and toxicologic studies of native corn in flour and bread].

During the bread-baking process, total alkaloid content is reduced by about 50%, the pharmacologically active alkaloids (the '-in' types) being reduced to a much greater extent than the less active type ('-inin' type). Using ergotamin and ergokryptin as a basis, total alkaloid levels were calculated from the HPLC data; these results were in a good agreement with the total alkaloid content calculated from 13 individual ergot alkaloids. The changes in the alkaloid spectrum caused by pelletin are shown. In feeding experiments with growing, pregnant, and lactating mice, diets with 0%, 1% and 2% unbaked (MM) or baked (MB) rye ergot were compared for possible toxic effects on reproduction, using animals fed ad libitum or pair-fed controls. A mean ingestion of 3.6 mg of alkaloids/kg body weight per day (MM 2%) was maternally toxic and caused inhibition of conception and implantation. Feeding with 1.3 or 1.6 mg of alkaloids/kg body weight per day (MM 1% and MB 2%) during pregnancy had no significant toxic effect on the embryo or fetus, but resulted in gestation time being prolonged to about 10 h. During lactation, an intake of 2.9 and 3.0 mg of alkaloids/kg body weight per day (MM 1% and MB 2%) led to a considerable reduction in growth (up to 50%) in the young mice compared to the control animals fed ad libitum. Both the determination of total ergot alkaloid content and the feeding experiment indicate that the bread-baking process causes a reduction and consequently a detoxification of ergot alkaloids of about 50%.

Abnormalities, Drug-Induced↗
PubMed2000

Impact of lactation upon fertility in the New World primate capuchin monkey (Cebus apella).

In the present paper, we have studied the impact of lactation upon fertility in the capuchin monkey, Cebus apella, under laboratory conditions. Nursing females (ten females, 12 postpartum periods) presented lactational amenorrhea (first menses at 159.2 +/- 9.0 vs 42.6 +/- 5.8 days postpartum in five non-nursing females, seven postpartum periods). Plasma estradiol and progesterone concentrations during lactational amenorrhea were lower than those during the follicular phase of the menstrual cycle. Prolactin was higher than in non-nursing females at 31-60 days postpartum. Interbirth interval, studied in three non-nursing (four intervals) and six nursing females (eight intervals) lasted for 349.5 +/- 11.8 and 613.4 +/- 30.8 days, respectively. In non-nursing females, early recovery of the menstrual cycle was followed by a residual infertility (mating but no pregnancy) lasting 152.8 +/- 7.9 days. In nursing females, recovery of the menstrual cycle was followed by an extended residual infertility of 301.5 +/- 22.7 days. Thus, in the capuchin monkey, nursing prolongs the interbirth interval by inducing lactational amenorrhea and extending the residual infertility period.

Amenorrhea↗
PubMed1996

Creatine phosphate as the preferred early indicator of ischemia in muscular tissues.

Changes in creatine compounds, especially the creatine phosphate to creatine ratio (CrP/Cr), are more sensitive indicators than changes in other metabolites for early ischemia in the different muscular tissues of heart, small intestine, skeletal muscle, and aorta. Changes in adenine nucleotide ratios are buffered by CrP reserves and the absolute concentration of adenine nucleotides can vary greatly between different muscular tissues. Accumulation of lactate is indicative of ischemia, but is not as sensitive as the ratio of CrP/Cr, but may better indicate the duration of ischemia. Glycerol also accumulates in muscular tissues during prolonged ischemia, so that consideration of both lactate and glycerol levels together, might confer a better estimate of the duration of ischemia of different muscular tissues.

Adenine Nucleotides↗
PubMed1988

Comparative study of hormonal counterregulation during GCIIS-guided hypoglycemia tests using human proinsulin and human insulin (recombinant DNA).

Counterregulatory effect following administration of biosynthetic human proinsulin (BHPI) and human insulin (BHI) were compared during hypoglycemia standardized by means of a glucose controlled insulin infusion system (GCIIS). A total of 0.148 +/- 0.010 U/kg of BHPI had to be given by the GCIIS in order to obtain a minimal blood glucose (BG) of 26 +/- 2 mg/dl (means +/- SEM) at 43 +/- 2 min. In contrast, 0.083 +/- 0.004 U/kg of BHI were sufficient to produce a minimal BG of 21 +/- 1 mg/dl (n.s.) at 35 +/- 1 min. (P less than 0.005). Moreover, BHPI infusion resulted in prolonged hypoglycemia and delayed blood glucose recovery. On a molar basis, the acute BG lowering effect of BHPI was about 13% that of BHI (BHPI 3.94 +/- 0.27 vs. BHI 0.51 +/- 0.03 nmol/kg). Serum proinsulin after BHPI reached its maximum of 19.4 +/- 2 pmol/ml at 20 min. and still exceeded basal values markedly at the end of the test period at 240 min. Serum insulin peaked at 10 min. (162 +/- 47 microU/ml) and had already returned to basal values (7.5 +/- 1 microU/ml) after 45 min. No severe side effects were observed and there was no need for glucose administration, but clinical symptoms of hypoglycemia were more pronounced after BHPI. Compared to BHI, BHPI produced a higher cortisol peak (252 +/- 16 vs. 168 +/- 10 ng/ml), a more pronounced secretion of ACTH and GH as well as a stronger decline of serum potassium (3.20 +/- 0.06 vs. 3.58 +/- 0.08 mmol/l). Counterregulatory prolactin secretion did not differ significantly. Urinary epinephrine secretion following hypoglycemia after BHPI exceeded that after BHI (10.3 +/- 4.8 vs. 3.0 +/- 0.5 ng/120 min.). Serum lactate increase after BHPI was more prolonged (1.68 +/- 0.24 vs. 0.37 +/- 0.14 mmol/l at 120 min.). BHPI-induced inhibition of lipolysis, as determined by free fatty acid patterns, was delayed and less pronounced. Our results indicate that the observed more distinct glucose counterregulation is due to prolonged hypoglycemia rather than to any specific BHPI action on the hypothalamic-pituitary axis. We regard this as a consequence of the prolonged circulating and biological half-life. A preferential proinsulin action on the liver may play an additional role. Whether this "depot effect" may be beneficial in the treatment of diabetes mellitus remains to be established.

Adrenocorticotropic Hormone↗
PubMed1995

Incremental doses of dobutamine induce a biphasic response in dysfunctional left ventricular regions subtending coronary stenoses.

BACKGROUND: Dobutamine stress echocardiography has been proposed as a diagnostic tool to identify viable myocardium. How regional wall thickening responds to dobutamine in the ischemic or short-term hibernating myocardium has not been adequately defined. We hypothesized that regional wall thickening would improve initially and subsequently deteriorate with incremental doses of dobutamine in viable myocardial regions supplied by a stenotic coronary artery. This study was undertaken to determine whether this biphasic pattern of regional function characterizes the response of ischemic or hibernating myocardium to dobutamine and to explore the factors and mechanisms that determine this response. METHODS AND RESULTS: Twenty-six pigs in four groups were studied: a control group (n = 5) to assess the response of myocardium perfused by nonstenotic coronary artery to incremental doses of dobutamine, and three experimental groups with a left anterior descending coronary artery stenosis producing acute myocardial ischemia (n = 7), short-term myocardial hibernation for 90 minutes (n = 7), and short-term hibernation for 24 hours (n = 7) to determine the functional and metabolic response to dobutamine under these conditions. Regional coronary flow was reduced to 40% to 60% of baseline, with significant reductions of regional wall thickening as measured by two-dimensional echocardiography and sonomicrometers. An incremental dobutamine infusion from 2.5 to 25 micrograms.kg-1.min-1 increased wall thickening and coronary flow without lactate production in the control group. In the other three groups, during the incremental dobutamine infusion, regional wall thickening improved initially, from 11.4 +/- 7.5% to 19.8 +/- 11.4%, P < .01, at dobutamine doses of 2.5 to 10 (4.5 +/- 2.2) micrograms.min-1.kg-1 but deteriorated subsequently to 5.0 +/- 5.8% at the maximal dose of dobutamine of 12.6 +/- 4.1 micrograms.min-1.kg-1. The initial improvement of regional wall thickening was associated with a small increase in regional coronary flow (from 0.53 +/- 0.18 to 0.68 +/- 0.25 mL.min-1.g-1 myocardium, P < .05) and with regional lactate production. High doses of dobutamine did not further increase regional coronary flow but markedly increased lactate production and induced regional myocardial acidosis (pH 7.26 +/- 0.07). The biphasic pattern of response to dobutamine was observed in each of the three experimental groups. Both peak improvement and peak deterioration occurred earlier and at lower dobutamine dose levels in the group with acute ischemia compared with the group with short-term hibernation for 24 hours (P < .05). CONCLUSIONS: A biphasic response of wall thickening to incremental dobutamine with initial improvement and subsequent deterioration is characteristic of ischemic or short-term hibernating myocardium. The initial low-dose dobutamine infusion improved wall thickening in the ischemic or hibernating myocardial region to a modest level. This initial modest improvement was transient and at the expense of metabolic deterioration of myocardial ischemia, so that at higher doses during prolonged dobutamine infusion, wall thickening deteriorated, lactate accumulated, and myocardial acidosis developed.

Animals↗
PubMed1989

Effects on pseudopregnancy, pregnancy and interoestrous intervals of pharmacological suppression of prolactin secretion in female dogs and cats.

Cabergoline, a new ergoline derivative, is a potent prolactin inhibitor. In this review, results are combined from previously published and unpublished blind laboratory and open clinical studies with cabergoline in pseudopregnant, pregnant and lactating bitches, in bitches with normal and prolonged cycles, and in pregnant queens. Dose-response studies in nursing bitches, using puppy weight as an endpoint, revealed that a dose of 5 micrograms/kg/day orally (for 5 days) was the optimal dose with a minimum of side effects. This dose effectively lowered blood prolactin concentrations in pregnant bitches and was partly luteolytic during the 1st half of gestation, and fully luteolytic during the 2nd half of gestation. Consequently, pregnancies were terminated in the 2nd half of pregnancy in the bitch, and in the queen. Treatment successes with pseudopregnancy and true and false lactation, including cases of eclampsia, were greater than 90%. The same level of success was seen in bitches with prolonged cycles (anoestrus). A 7-10-day treatment period resulted almost uniformly in oestrus, and restored fertility in greater than 80% of all bitches mated. Cycles were occasionally shortened in bitches treated for false lactation. Attempts to shorten cycles routinely in beagle bitches, in a commercial breeding operation, with a dose of 5 micrograms/kg/day for 14 days during months 4, 5 or 6 of the cycle were unsuccessful.

Abortion, Spontaneous↗
PubMed1983

Prolonged exercise in highly trained female endurance runners.

The effects of prolonged exercise in a 21 degree C dry bulb and 15 degree C wet bulb environment at 65%-70% VO2max were examined in seven highly trained females. The subjects, aged 22-35 years, underwent an initial incremental treadmill test to exhaustion, with assessment of VO2max and related cardiorespiratory variables. One week later, under similar environmental conditions, subjects ran at approximately 65% VO2max for 80 min on a motor-driven treadmill. Approximately 10 ml of venous blood was withdrawn 10 min prior and immediately prior to the onset of prolonged exercise, and at 20, 40, 60, and 80 min, and 20 min post-exercise. Venous blood was analyzed for glucose, lactate, osmolality, Na+, K+, protein, and hemoglobin (Hb). Hematocrit was measured and changes in plasma volume calculated. VO2, VE, respiratory exchange ratio, and heart rate were recorded at 17, 37, and 77 min. The percent body fat estimated from skinfold thicknesses was 19 +/- 1%. The mean VO2max was 59.3 +/- 1.0 ml . kg-1 . min-1, with a mean max VE STPD and heart rate of 78.75 +/- 3.10 1 . min-1 and 175 +/- 4 beats . min-1, respectively. No significant changes occurred in VO2, VE, % VO2max, heart rate, venous lactate, plasma glucose, or plasma protein during the prolonged exercise. A significant decrease in respiratory exchange ratio was noted. Significant changes also occurred in hematocrit, Hb, Na+, K+, and osmolality. An interesting finding was the pre-exercise expansion of the plasma volume.

Adipose Tissue↗