Developmental effects of intraperitoneal saline injections in neonatal rats

The response to neonatal intraperitonal (IP) saline injections was investigated in neonatal male and female rats from split- and whole-litters. The results demonstrate that male or female rats housed under split-litter conditions and subjected to daily IP injections during the early neonatal period have the same body weight and plasma corticosteroid and testosterone (males only) levels as littermate controls. On the other hand, treated male and female animals from whole-litters weigh significantly less than controls. Additionally, plasma testosterone and cortisteroids from treated males did not differ from controls at any age tested, but treated females from whole-litters had significantly elevated corticoids at days 100 and 150 when compared to controls. These results suggest that when doing developmental studies involving IP injections, it would be advisable to house animals under split-litter conditions.     

A new method for giving repetitive intraperitoneal injections to neonatal rats

This report describes a new method for giving repetitive intraperitoneal injections to neonatal rats. The hypodermic needle is passed through the muscle layer of the flank directly into the peritoneal cavity in contrast to the conventional approach. In a trial using 20 neonatal rats aged 1 day, no leakage of the inoculated physiological saline occurred, and there was no associated morbidity or mortality of these rats.     

Insensitivity of some rats to intraperitoneal injections of collagenase and trypsin

In the rat peritoneal injections of collagenase or trypsin give rise to severe lesions. In our experience 20% of the animals remain intact. The frequency of lesions increases with older and heavier subjects. Moreover 25% of the rats who remained free of lesions after a first injection of collagenase resist to a second one. This shows that they are strongly protected against the enzyme. The exact nature and location of this protective mechanism are not known.     

Taurine concentration in the brain and in the plasma following intraperitoneal injections

Summary. The effect of different taurine doses (0.050, 0.125, 0.250, 0.500 and 1.000g/kg) administered intraperitoneally to Wistar rats was studied in both the plasma and the hippocampal microdialysate content.The samples were analyzed by reverse phased HPLC for the microdialysate samples and by HPLC with ion-exchange post-column derivatization (ninhydrin) for the plasma samples.In both plasma and microdialysate, we observed a dose dependent increase of taurine concentration. The AUC curves obtained from both microdialysate and plasma samples showed that the increase of taurine concentrations were linear. The mean ratio between AUCs microdialysate and plasma was 1.63±0.21 showing thus an unbalance between plasma and brain taurine content; a mechanism which enhance taurine transfer from the plasma to the brain was assumed.     

Urinary corticosterone levels in mice in response to intraperitoneal injections with saline

The concept of refinement is an important issue in the field of laboratory animal science. Refinement-based research aims to improve animal welfare, to increase the reliability of experimental outcome, and to diminish variation. In search of refinement of experimental techniques, this study investigated whether urinary corticosterone can be used as a noninvasive measure of acute stress in mice.     

Repeated microsphere injections in rats

There is currently some question concerning the dose of microspheres and blood sample withdrawal rates which will give accurate reproducable tissue blood flow measurements. In these experiments unanesthetized male Sprague-Dawley rats were tested with repeated injections of 100,000 15±5μ microspheres to monitor the effect on cardiovascular and regional hemodynamic measurements. No significant change in blood pressure, cardiac output or tissue blood flow was seen with up to 3 repeated injections of 100,000 microspheres per injection. In addition, no difference was observed between blood sample withdrawal rates of 0.4 or 0.8 ml/min. These data are consistent with previous reports that over 300,000 microspheres can be injected into the rat with no measurable change in hemodynamics and that accurate tissue blood flow measurements are dependent on an adequate number of microspheres being trapped in the reference blood and tissue samples rather than the rate of blood withdrawal.     

A pathophysiological study of abdominal organs following intraperitoneal injections of chloral hydrate in rats: comparison between two anaesthesia protocols

Chloral hydrate (CH) is used as an anaesthetic agent in laboratory rats. Side effects occurring with high concentrations have mainly occurred in abdominal organs. The objective of the present study was to minimize these side effects following intraperitoneal administration of CH using lower concentrations. Animals were evaluated using different procedures including a general necropsy, intraperitoneal white cell counts, histology and duodenal peristalsis and acetylcholine-induced contractions. Results clearly show that lower concentrations of CH while keeping the same anaesthetic dose (400 mg/kg) will minimize the irritancy of CH on abdominal organs while providing the same level of anaesthesia.     

Phosphatidylserine binding sites in erythroid spectrin: location and implications for membrane stability

The erythrocyte membrane is a composite structure consisting of a lipid bilayer tethered to the spectrin-based membrane skeleton. Two complexes of spectrin with other proteins are known to participate in the attachment. Spectrin has also been shown to interact with phosphatidylserine (PS), a component of the lipid bilayer, which is confined to its inner leaflet. That there may be multiple sites of interaction with PS in the spectrin sequence has been inferred, but they have not hitherto been identified. Here we have explored the interaction of PS-containing liposomes with native alpha- and beta-spectrin chains and with recombinant spectrin fragments encompassing the entire sequences of both chains. We show that both alpha-spectrin and beta-spectrin bind PS and that sites of high affinity are located within 8 of the 38 triple-helical structural repeats which make up the bulk of both chains; these are alpha8, alpha9-10, beta2, beta3, beta4, beta12, beta13, and beta14, and PS affinity was also found in the nonhomologous N-terminal domain of the beta-chain. No other fragments of either chain showed appreciable binding. Binding of spectrin and its constituent chains to mixed liposomes of PS and phosphatidylcholine (PC) depended on the proportion of PS. Binding of spectrin dimers to PS liposomes was inhibited by single repeats containing PS binding sites. It is noteworthy that the PS binding sites in beta-spectrin are grouped in close proximity to the sites of attachment both of ankyrin and of 4.1R, the proteins engaged in attachment of spectrin to the membrane. We conjecture that direct interaction of spectrin with PS in the membrane may modulate its interactions with the proteins and that (considering also the known affinity of 4.1R for PS) the formation of PS-rich lipid domains, which have been observed in the red cell membrane, may be a result.     

Bone aluminum uptake in uremic rats receiving intraperitoneal iron

To assess the effect of concomitant iron and aluminum loads on bone aluminum accumulation and on the response to the deferoxamine test in rats with the same aluminum surcharge, Wistar rats with chronic renal failure were divided into three groups: iron-overloaded rats (N=6) (intraperitoneal iron); iron-depleted rats (N=6) (blood withdrawal two to three times per week); control rats (N=4) (no manipulation). All groups received intraperitoneal aluminum simultaneously. After 6 wk, a deferoxamine challenge test was performed. Thereafter, bone aluminum and iron were measured. The iron-overloaded rats showed higher bone iron content (iron overloaded: 147.7±55.4 μg/g; iron depleted: 7.9±1.0, and controls 13.3±9.9 μg/g, p<0.010) and lower bone aluminum content (iron overloaded: 14.2±4.0 μg/g; iron depleted: 70.9±35.1 μg/g; controls: 72.7±28.3 μg/g p<0.005). No differences were found between the iron-depleted and control rats. After the deferoxamine infusion, the iron-depleted rats tended to have higher serum aluminum increments (p=NS) and higher urinary aluminum excretion (p<0.012, p<0.020) than control rats despite similar amounts of aluminum in bone of the two groups. Aluminum bone accumulation was minor if iron and aluminum loads were given concomitantly. The iron depletion influenced the results of the deferoxamine challenge test in rats with similar bone aluminum burden.     

Tissue distribution and metabolism of guanosine in rats following intraperitoneal injection

Guanosine has long been known as an endogenous purine nucleoside deeply involved in the modulation of several intracellular processes, especially G-protein activity. More recently, it has been reported to act as an extracellular signaling molecule released from neurons and, more markedly, from astrocytes either in basal conditions or after different kinds of stimulation including hypoxia. Moreover, in vivo studies have shown that guanosine plays an important role as both a neuroprotective and neurotrophic agent in the central nervous system. Specific high-affinity binding sites for this nucleoside have been found on membrane preparations from rat brain. The present study was undertaken to investigate the distribution and metabolic profiles of guanosine after administering the nucleoside to gain a better understanding of the biological effects of this potential drug candidate. Rats were given an intraperitonal (i.p.) injection of 2, 4, 8 or 16 mg/kg of guanosine combined with 0.05% of [3H]guanosine. Plasma samples were collected 7.5, 15, 30, 60 and 90 min after the guanosine-mixture administration and analyzed by either a liquid scintillation counter or by HPLC connected to a UV and to an on-line radiochemical detector to measure the levels of guanosine and its metabolic products guanine, xanthine and uric acid. The levels of guanosine, guanine and xanthine were also measured in brain, lung, heart, kidney and liver tissue homogenates at the defined time points after the injection of 8 mg/kg of the guanosine-mixture. We found that the levels of radioactivity in plasma increased linearly in a dose- and time-dependent manner. Guanosine was widely distributed in all tissues examined in the present study, at almost twice its usual levels. In addition, guanine levels dramatically increased in all the organs. Interestingly, enzymatic analysis of the plasma samples showed the presence of a soluble purine nucleoside phosphorylase, a key enzyme in the purine salvage pathway and nucleoside catabolism. Since guanosine has been shown to be neuroprotective and astrocytes have been reported to play critical roles in mediating neuronal survival and functions in different neurodegenerative disorders, we also performed uptake and release.