Differences between the sexes and the effects of surgery and anesthesia on the urinary excretion rate of eicosinoids in the rat

Measurements were made of PGE2, PGF2 and TXB2 in the urine of male and female Munich-Wistar rats. Initial urine were collected in the awake state in metabolic cages and were followed by collections of ureteral urine during surgery and anesthesia both before and during cyclooxygenase inhibition with indomethacin. The excretion rate of all eicosinoids in the awake state was similar between the sexes. PGE2 excretion remained unaffected after anesthesia/surgery in both sexes indicating that providing plasma volume is maintained, the PGE2 system is not activated by the stress of anesthesia/surgery. Near complete inhibition of PGE2 was observed during indomethacin administration in both sexes. TXB2 excretion rates rose in both males and females with anesthesia/surgery and were slightly suppressed during indomethacin in males only. PGF2 excretion rose following surgery/anesthesia and was statistically significant in female rats. During indomethacin, TXB2 excretion was moderately reduced in male rats and unaffected in the female. Near complete inhibition of PGF2 was observed during indomethacin in both sexes. The urinary eicosinoid responses to indomethacin seen in these studies failed to provide an explanation for our earlier observations of a fall in renal vascular resistance in the female rat, studied under anesthesia and during indomethacin administration.     

The influence of urinary flow rate on mercury excretion in children

ProjectThere is limited literature concerning the effect of urinary flow rate on mercury excretion at low-level exposure. The aim of the present study is to examine the influence of urinary flow rate on mercury excretion in children. Also of interest is the influence of flow rate on creatinine excretion and creatinine-corrected mercury, which arisearises with spot urine samples.ProcedureA substudy of the New England Children's Amalgam Trial collected pairs of urine samples from children aged 10–16 years: a timed overnight collection and a spot daytime sample collected the following day. These samples were analyzed for mercury and creatinine concentration. Regression analysis was used to model the effect of urinary flow rate in the timed overnight samples. A paired t-test compared concentrations and creatinine-corrected mercury between overnight and daytime samples.ResultsCreatinine excretion rate (mg/h) increased significantly with urinary flow rate (mL/h), whereas creatinine concentration (g/L) decreased with flow rate. We found a non-significant increase in mercury excretion rate (ng/h) with flow rate, and mercury concentration decreased with flow rate. Mercury and creatinine concentrations were significantly higher in the overnight compared to daytime samples. For creatinine-corrected mercury, no significant impact of urinary flow rate was found.ConclusionsAlthough the creatinine excretion rate, and probably the mercury excretion rate, increased with urinary flow rate, the mercury/creatinine ratio seemed relatively unaffected by urinary flow rate.     

Corticosterone is converted to 6 beta-hydroxycorticosterone in rat: effects of the metabolite on urinary electrolyte excretion

This study was performed to determine whether corticosterone (B), the major glucocorticoid of rat, is metabolized to its 6 beta-OH derivative (6 beta-OH-B) and whether this derivatives has any effects on Na+ or K+ transport in rat kidney. Normal and adrenalectomized (adx) rats were injected with [3H]B and urine was collected for 5 h and examined for metabolites of B. Metabolites were collected by solid phase extraction on mu Bondapak C18 cartridges and fractionated by reversed phase high performance liquid chromatography. Fractions coeluting with 6 beta-OH-B were rechromatographed by normal phase thin layer chromatography. Approximately 5% of the radioactivity recovered from the urine of both intact and adx rats cochromatographed with 6 beta-OH-B on the two systems. Mass spectra of this fraction were virtually identical to those of authentic 6 beta-OH-B, demonstrating that rats do metabolize B to its 6 beta-OH derivative. To evaluate the biological activity of this metabolite, adx rats were injected with NaCl and KCl and with varying dosage of either 6 beta-OH-B or reference steroids (aldosterone, B, 6 beta-OH-F). 6 beta-OH-B produced a significant antinatriuresis at all doses. Kaliuresis occurred only at the highest dose and creatinine excretion increased, suggesting increased glomerular filtration from a glucocorticoid effect. Although 6 beta-OH-B may simply be exerting mineralo- and glucocorticoid actions there are two unexplained findings. First, 6 beta-OH-B (10 micrograms/100 g) significantly decreased urinary K excretion with associated antinatriuresis, an effect which has not been seen with Aldo administration. Second, neither a kaliuretic nor antinatriuretic effect of 6 beta-OH-B could be demonstrated in experiments using a method to enhance mineralocorticoid induced K+ excretion (K+ deprivation and NaCl loading only). Yet, the dose used was clearly antinatriuretic in the initial bioassay. It is concluded that the rat is capable of metabolizing B to its 6 beta-OH-B derivative which appears in substantial quantity in the urine. This metabolite produces antinatriuresis in the adrenalectomized rat.     

Effect of fasting on urinary excretion of water and nitrogen in the rat

Rats housed in metabolic cages undergoing 48 h fasting showed reduced daily intake of drinking water and increased urinary volume. Both the daily amount of urinary creatinine and urea excreted were diminished with fasting, while that of ammonia was augmented. Besides demonstrating metabolic water loss under fasting, results suggest that ammonia derived from glutamine in the kidney, rather than urea formed in the liver, is the main nitrogenous catabolic product of amino acids in fasting.     

Renal metabolism and urinary excretion of platelet-activating factor in the rat

The origin of platelet-activating factor (PAF) in the urine remains ill defined. The present study documents that [3H]PAF (3.5 mu Ci) injected into the renal artery of isolated control rat kidney preparations perfused at constant pressure with a cell-free medium containing 1% bovine serum albumin (BSA) was excreted in negligible amounts (0.034%) in the urine, whereas 6% was retained by the kidney. When kidneys were perfused with a BSA-free medium, 0.029 and 71% of the total radioactivity added to the perfusate was recovered in the urine and in the renal tissue, respectively. [3H]PAF urine excretion in proteinuric kidneys from adriamycin-treated rats was still negligible (0.015%). Analysis of the renal tissue-retained radioactivity in control and proteinuric kidneys perfused with 1% BSA indicated metabolism into long chain acyl-sn-glycero-3-phosphorylcholine species, lyso-PAF, glycerols, and intact PAF. Thin layer chromatography analysis of [3H]glycerol fraction in these renal extracts showed two major components comigrating with 1-O-alkylglycerol and 1-O-alkyl-2-fatty acylglycerol. Isolated proximal tubules, but not glomeruli from nephrotic rats exposed to increasing concentrations of BSA (0-4%), had a higher PAF uptake than control tubules for BSA concentrations ranging from 0 to 0.1%. Our findings in the isolated perfused kidneys indicate that, in normal conditions, circulating PAF is excreted in the urine in negligible amounts and that the altered glomerular permeability to proteins does not affect this excretion rate. Moreover, analysis of renal tissue radioactivity documented that the renal metabolism of PAF is comparable in control and nephrotic kidneys.     

Silicic acid: its gastrointestinal uptake and urinary excretion in man and effects on aluminium excretion

Silicon (Si), as silicic acid, is suggested to be the natural antidote to aluminium (Al) toxicity, and was recently shown to promote the urinary excretion of Al from body stores. The metabolism of Si in man, however, remains poorly investigated. Here we report on the pharmacokinetics and metabolism of Si in healthy volunteers following ingestion of orthosilicic acid (27-55 mg/l Si) in water. We also investigated whether orthosilicic acid promotes the urinary excretion of endogenous Al. Minimum, median uptake of Si from the ingested dose was 50.3% (range: 21.9-74.7%, n = 8) based on urinary analysis following dosing. Significant correlations were observed between creatinine clearance and Si levels in serum or urine (r = 0.95 and 0.99, respectively). Renal clearance of Si was 82-96 ml/min suggesting high renal filterability. These results suggest that orthosilicic acid is readily absorbed from the gastrointestinal tract of man and then readily excreted in urine. There was no significant increase in Al excretion, over 32 h, following ingestion of the orthosilicic acid dose (P = 0.5; n = 5).     

Sex modifies genetic effects on residual variance in urinary calcium excretion in rat (Rattus norvegicus)

Conventional genetics assumes common variance among alleles or genetic groups. However, evidence from vertebrate and invertebrate models suggests that residual genotypic variance may itself be under partial genetic control. Such a phenomenon would have great significance: high-variability alleles might confound the detection of "classically" acting genes or scatter predicted evolutionary outcomes among unpredicted trajectories. Of the few works on this phenomenon, many implicate sex in some aspect of its control. We found that female genetic hypercalciuric stone-forming (GHS) rats (Rattus norvegicus) had higher coefficients of variation (CVs) for urinary calcium (CV = 0.14) than GHS males (CV = 0.06), and the reverse in normocalciuric Wistar-Kyoto rats (WKY) (CV(♂) = 0.14; CV(♀) = 0.09), suggesting sex-by-genotype interaction on residual variance. We therefore investigated the effect of sex on absolute-transformed residuals in urinary calcium in an F(2) GHS × WKY mapping cohort. Absolute residuals were associated with genotype at two microsatellites, D3Rat46 (RNO3, 33.9 Mb) and D4Mgh1 (RNO4, 84.8 MB) at Bonferroni thresholds across the entire cohort, and with the microsatellites D3Rat46, D9Mgh2 (RNO9, 84.4 Mb), and D12Rat25 (RNO12, 40.4 Mb) in females (P < 0.05) but not males. In GHS chromosome 1 congenic lines bred onto a WKY genomic background, we found that congenic males had significantly (P < 0.0001) higher CVs for urinary calcium (CV = 0.25) than females (CV = 0.15), supporting the hypothesis of the inheritance of sex-by-genotype interaction on this effect. Our findings suggest that genetic effects on residual variance are sex linked; heritable, sex-specific residuals might have great potential implications for evolution, adaptation, and genetic analysis.     

Flight metabolic rate has contrasting effects on dispersal in the two sexes of the Glanville fritillary butterfly

Evolution of dispersal is affected by context-specific costs and benefits. One example is sex-biased dispersal in mammals and birds. While many such patterns have been described, the underlying mechanisms are poorly understood. Here, we study genetic and phenotypic traits that affect butterfly flight capacity and examine how these traits are related to dispersal in male and female Glanville fritillary butterflies (Melitaea cinxia). We performed two mark–recapture experiments to examine the associations of individuals’ peak flight metabolic rate (MR_peak) and Pgi genotype with their dispersal in the field. In a third experiment, we studied tethered flight in the laboratory. MR_peak was negatively correlated with dispersal distance in males but the trend was positive in females, and the interaction between MR_peak and sex was significant for long-distance dispersal. A similar but nonsignificant trend was found in relation to molecular variation at Pgi, which encodes a glycolytic enzyme: the genotype associated with high MR_peak tended to be less dispersive in males but more dispersive in females. The same pattern was repeated in the tethered flight experiment: the relationship between MR_peak and flight duration was positive in females but negative in males. These results suggest that females with high flight capacity are superior in among-population dispersal, which facilitates the spatial spreading of their reproductive effort. In contrast, males with high flight capacity may express territorial behaviour, and thereby increase the number of matings, whereas inferior males may be forced to disperse. Thus, flight capacity has opposite associations with dispersal rate in the two sexes.     

Testosterone urinary excretion rate increases during hypergravity in male monkeys

Real and simulated microgravity impairs T secretion both in animals and in the human. To verify whether hypergravity might enhance T secretion as a consequence of an opposite mechanical effect, 6 male monkeys were centrifuged at 2 G for 3 weeks after a 1 G stabilization period lasting 3 weeks and then taken back to 1 G for 1 week and urine were collected daily for T excretion measurement. Significantly higher level were observed during the initial 2 G phase as compared to pre- and post centrifugation periods and the trend was the same during the remaining 2 G period. This may reflect changes in testicular perfusion rather than endocrine adaptation per se.     

The relationship between respiratory sinus arrhythmia and heart rate during anesthesia in rat.

During inspiration the heart rate (HR) increases and during expiration it decreases. Contribution of respiratory sinus arrhythmia (RSA) to spontaneous heart rate variability (HRV) can be measured as the high frequency (HF) component of variation in consecutive R-R intervals on ECG. In conscious rats, slowing of HR is associated with an increase in HF. The aim of this study was to investigate whether this relationship between HF and HR is preserved during anesthesia in rat. A 15 minutes long ECG signal was recorded from rats (N=15) under moderate chloral hydrate (CHL) anesthesia. Recordings were extended with 45 minutes to investigate the effect of atropine (N=3), against controls (N=3). Short term HRV was investigated in 30 seconds long epochs. HF was considered the frequency band between 0.8 and 1.6 Hz. RSA was quantified as the relative spectral power of the HF. Respiratory frequency (RF) was quantified as the mean spectral frequency within the HF band. One minute estimates of HR, RSA and HF were calculated by averaging 3 epochs of 30 seconds overlapped 50%. The average HR was 427 +/- 3 bpm. The magnitude of RSA was 45 +/- 1% at a RF of 71 +/- 1 rpm. We found that: (1) the decrease in HR that occurs during CHL anesthesia in rat correlates with an increase in RSA; (2) atropine reduces RSA and the time-dependent decrease in HR; (3) the time-dependent increase in RSA is preserved after atropine. We conclude that the correlation between RSA and HR reflects the cardio-pulmonary coupling under parasympathetic control.     

Differences in environmental response between the sexes of the dioecious shrub Baccharis halimifolia (Compositae)

Summary Baccharis halimifolia (Compositae) is a dioecious shrub which grows on the upland fringe of tidal marshes along the Atlantic and Gulf Coasts of North America. We examined the responses of the two sexes to variation in nutrient and moisture availability plant density, and defoliation. By growing plants from seedlings to flowering adults under various combinations of soil type, fertilization rate and plant density, we were able to establish different rates of plant growth and mortality. Plants grown at high density and low nutrient and water supply grew the least, incurrent the most mortality and showed a male-biased sex ratio (73% male). At low density with abundant nutrients and water, plants grew more, survived well, flowered frequently, and were female-biased (75% female). Changes in sex ratio were probably the result of sex-related mortality rather than sexual lability of the seedlings. While changes in sex ratio occurred under experimental conditions in the green-house, no evidence for differences in habitat utilization between the sexes were found in the field and the sex ratio (59% female) did not vary across habitats. In the marsh habitats we sampled where water and nutrients were apparently available, there was no evidence for differential mortality between the sexes. When defoliated (75% of leaf tissue), both sexes showed similar reductions in reproductive effort (number of flower heads/shoot). Our results indicate that differences between the sexes of Baccharis in their response to environmental growing conditions is an important ecological factor associated with the separation of male and female function into separate individuals.