Effect of high plant (cowpeas) and animal (casein) proteins on urinary –N-acetyl-beta-D- glucosaminidase (NAG) and micoalbuminuria in rats

Background: Urinary NAG activity is one of the most frequently evaluated urinary enzymes used in the diagnosis of renal tubular toxicity in recent time. Urinary NAG activity has been reported to precede changes in serum creatinine and endogenous creatinine clearances while microalbumin is the excretion of albumin in urine; this is highly variable, ranging from non detectectable quantities to milligrams of albumin. The aim of this study is to determine the effect of the intake of high plant (Cowpeas) and animal (Casein) proteins on urinary NAG and microalbuminuria in rats.Methods: One hundred and eighty wistar rats were used in this study. The rats were randomly distributed into 8 experimental groups (20 per group) and control (20). Blood and 24 hour urine samples were collected at baseline, 1 month, 3 months and 6 months intervals. Urinary NAG and microalbumin were determined spectrophotometrically.Results: Urinary NAG concentration was observed to be significantly higher (P<0.01) in urine of rats on casein diets when compared to baseline values, increases of over tenfold were observed. When NAG values of cowpeas fed rats was compared to that of casein fed rats, there was a significant increase (P<0.01) in urinary NAG values of rats fed with casein diet and the increase seen was proportional to dosage and duration. However for urinary microalbumin concentration, there was a significant increase in urinary microalbumin concentration of 30% casein fed rats when compared to baseline at 1month (P<0.05), which dropped at 3 months and 6 months and for the 40% casein diet, there was a significant increase (P<0.01) at 1 and 3 months but dropped at 6 months. Values of 30% cowpeas fed rat were significantly higher (P<0.01) than baseline values at 1 month and at 3 months for 35% cowpeas fed rats. Others were not significant.Conclusion: This study has clearly shown that the intake of a high plant protein, cowpeas leads to mild increase in NAG and microalbumin in urine. On the other hand, an intake of high casein diet, an animal protein, resulted in a marked increase in urinary NAG and mild increase in microalbumin. This study has also shown that the increase of urinary NAG precedes that of microalbumin.Keywords: High-protein diet, Urinary NAG, Microalbumi

Circadian changes in urinary Na+/K+ ratio in humans: is there a role for aldosterone?

Background: There are indications that the renal excretion of Na+ and K+ is affected by the body's circadian rhythm. Aldosterone is known to be the major determinant of urinary Na+/K+ ratio. However, recent reports suggest that the circadian rhythm of K+ excretion does not depend on endogenous aldosterone. We therefore aimed to investigate the diurnal and nocturnal changes in urinary Na+/K+ ratio, and to test if aldosterone plays a key role.Methods: We investigated the Na+/K+ ratios and aldosterone excretion in 12h-day and night urine. Ethical approval was obtained for 24 healthy male subjects, aged 20-30 years, who were included in this study. 12h-day and 12h-night urine samples were collected. Urine concentrations of Na+ and K+ were analysed using flame photometry and the amount in mmol of these electrolytes was calculated. Urine aldosterone concentrations were analysed using the enzyme immunoassay method. Urinary Na+/K+ ratios were calculated by dividing the amount of Na+ by that of K+, both in mmol/12h. Results are presented as mean ± SEM, and analysed using unpaired Student’s t-test.Results: While a significantly higher Na+/K+ ratio was observed in the 12h-night urine compared with the 12h-day urine (4.22 ± 0.18 vs 2.91± 0.18, p<0.001, n=24), aldosterone excretion (μg/12h) was similar in both the day and night urine.The significantly increased Na+/K+ ratio in the nighttime urine observed in this study was shown to be as a result of a significant decrease (p<0.001) in K+ excretion at night. Correlation analysis revealed no significant relationships between aldosterone and the Na+/K+ ratio in both the day and night urine.Conclusion: Our results suggest that an aldosterone independent mechanism may be responsible for the night time dip in the renal excretion of K+. Understanding this mechanism will provide more insights into how this pathway may be targeted in hypertension caused by non-dipping night time renal K+ excretion.Keywords: Na+, K+, Na+/K+ ratio, aldosterone, 12h-day, 12h-night, urin

Thirst perception, drinking, arginine vasopressin activity and associated neurohumoral factors

Thirst, drinking, and arginine vasopressin (AVP) secretion are essential correlated osmoregulatory mechanisms that are crucial for normal physiologic function and overall survival of humans. These homeostatic mechanisms require or are operated via complex central and peripheral neural connections with influence from other peptides and hormones including angiotensin II, atrial natriuretic peptide and relaxin. The effectiveness of these mechanisms declines with age, and the consequences manifest during hyperosmotic challenges as decreased thirst and urine concentrating ability. The neurohumoral cascades involved in the physiological response to alterations in fluid and electrolyte balance are examined.Keywords: Thirst perception, drinking, arginine vasopressin, angiotensin II, atrial natriuretic peptide, relaxi

Effects of corn silk aqueous extract on intraocular pressure of ocular hypertensive human subjects

Stigma/style of Zea mays L (Corn silk) has been documented to have hypotensive effect on blood pressure and to relieve oedema. However we are not aware of any literature on its hypotensive effect on intraocular pressure (IOP) of humans or animals. We studied the effects of water only, masked doses of corn silk aqueous extract (60 mg/kg, 130 mg/kg, 192.5 mg/kg and 260 mg/kg body weight) on the IOP and blood pressure (BP) of twenty normotensives and twenty ocular hypertensive subjects. Also we compared the effects of the varied doses of corn silk aqueous extract (CSAE) with masked doses (5 mg/kg and 10 mg/kg body weight) of acetazolamide on IOP of ocular hypertensive subjects only. The results showed that the last three doses of CSAE lowered IOP and BP significantly (p<0.001) within eight hours of administration. The peak effect on IOP was observed after four hours while the peak effect on BP was observed after three hours of administration in the normotensives and ocular hypertensive subjects likewise the hypotensive effect was dose-dependent. The results also showed that 130 mg/kg body weight of CSAE produced the same hypotensive effect on IOP of ocular hypertensive subjects as 5 mg/kg body weight of acetazolamide. Therefore CSAE may have some IOP lowering effects that require further investigation in the management of ocular hypertension. (S Afr Optom 2013 72(3) 133-143

Thirst perception in dehydrated sickle cell disease patients in steady state

Liberal fluid intake is one of the key management strategies in sickle cell anaemia (SCA) patients in steady state, but less work has been done on the desire of patients to drink water. Using the Visual Analogue Scale we studied thirst perception (TP) in 20 euhydrated SCA patients and 28 control (HbA) subjects, as well as during dehydration in 13 SCA patients and 9 HbA subjects. Serum and urine samples were collected and analyzed for Na, K ions, creatinine concentrations and haematocrit and specific gravity of urine were determined. During euhydration, TP was significantly [

Thirst Perception and Dryness of Mouth in Healthy Young Adults Nigerians

This study examined the threshold for thirst perception (TP) using the visual analogue scale (VAS). Thirst perception (TP) and dryness of mouth (DM) were studied in normal subjects, (n = 137; 78 males of height, 1.72 ± 0.01, age, 23 ± 0.26, body mass index, 21.11 ± 0.29, and 59 females of height, 1.65 ± 0.01, age, 21 ± 0.23, body mass index, 21.0 ± 0.27). The results showed that (i) TP and DMin males, (1.21 ± 0.15 cm and 1.14 ± 0.16cm respectively) and in females, (1.10 ± 0.16cm and 1.04 ± 0.17cm respectively) were similar. (ii) The relationship, Thirst (cm) = 0.75 (plasma arginine vasopressin ± 1.2) exists and has a mean of not thirsty of 1.2cm at the lower end of the scale. (iii) The plasma osmolality of 281mOsm/kg cannot be the threshold for TP and the plasma osmolality of 285mOsm/kg or 284.3mOsm/kg cannot be the threshold for plasma arginine vasopressin secretion but rather the mean of the lower set point of the scales for TP and plasma arginine vasopressin [PAVP] secretion. (iv) The threshold for TP using the VAS is between 1.50 - 1.575cm markings, and plasma osmolality of 286.0 - 286.25 mOsm/kg. PAVP of 0.4 – 0.5 pmol/l being the sensitivity of the osmoregulatory unit

Osmoregulatory adaptations during lactation : thirst, arginine vasopressin and plasma osmolality responses

Pregnancy and lactation are accompanied by an increase in circulating blood volume secondary to a 10 mOsmol/kgH20 decrease in plasma osmolality, decrease in the osmotic threshold for thirst and arginine vasopressin (AVP) release, prolactin-induced AVP, oxytocin and aldosterone release, as well as increased water intake and retention. The increased blood volume as a result of increased thirst; drinking and fluid retention could be beneficial for milk production and secretion during lactation. Furthermore, AVP can directly initiate milk ejection similar to oxytocin by interacting with both vasopressin and oxytocin receptors located in myoepithelial cells of the mammary gland. This review explores how osmotic equilibrium is maintained during lactation through changes in thirst, AVP release and plasma osmolality; and highlights the potential role of AVP in milk secretion

Streptozotocin diabetes and insulin resistance impairment of spermatogenesis in adult rat testis: central Vs local mechanism

Mammalian reproduction is dynamically regulated by the pituitary gonadotropins, luteinizing hormone (LH) and follicle-stimulating hormone (FSH). These hormones are synthesized in the pituitary gland following stimulation by the gonadotropin-releasing hormone (GnRH) and act by stimulating steroid production and gametogenesis in both males and females. Male adult Sprague-Dawley rats (120 – 140 g) were randomly divided into 7 groups. Group 1 > Control group; fed on normal rat pellets. Group 2 > Streptozotocin group; received a single dose IP injection of streptozotocin 45 mg/kg BW in Na+ citrate buffer pH 4.5. Group 3 > Streptozotocin-insulin treated group; received a single dose IP injection of streptozotocin as in group 2 above and treated with insulin sub-cutaneously. Group 4 > Streptozotocin-ginger treated group; received a single dose IP injection of streptozotocin as in group 2 above and treated with 500 mg/Kg Ginger extract orally. Group 5 > Insulin resistant group; fed ad libitum on a special diet containing 25% fructose mixed with 75% normal rat chow (w/w). Group 6 > Insulin resistant-pioglitazone treated group; fed ad libitum on a special diet as in group 5 above and treated with Pioglitazone 15 mg/kg orally. Group 7 > Insulin resistant-ginger treated group; fed ad libitum on a special diet as in group 4 above, and also treated with 500 mg/Kg Ginger extract orally. Hormonal and tissue biochemistry analyses revealed that both central and local mechanisms are implicated in the impairment of spermatogenesis by diabetes but the hypothalamo-pituitary testicular axis alteration might not likely have a major impact as the local defect on steroidogenesis in the testis. This local defect could also predispose to male hypogonadism, i.e. failure of gonadal function