The development of gluconeogenic enzymes in the liver and kidney of fetal and newborn foals.

The activities of glucose-6-phosphatase (G6P), fructose diphosphatase, phosphoenolpyruvate carboxykinase (PEPCK), aspartate and alanine transferases were measured in liver and kidney of fetal foals between 100-318 days of gestation (term approximately 335 days) and during the immediate postnatal period (0-48 h after birth). All 5 enzymes could be detected in the fetal liver and kidney at the youngest gestational age studied. Mean fetal activities were lower than those observed in their mothers and showed no change with gestational age for the majority of enzymes studied. However, renal PEPCK and renal and hepatic G6P did increase towards term. At birth, hepatic and renal activities of these two enzymes were higher than those found in late gestation or in the adult animals. There was no apparent change in the activities of any of the other enzymes at birth. In late gestation (80-90% gestation), the activities of G6P and PEPCK in the foal were low compared to those in other species at the same stage of gestation. Similarly, the perinatal increase in enzyme activity occurred closer to term in the foal than in most other species. These observations indicate that maturation of glucogenic capacity occurs relatively late in the fetal foal and suggests that this process may be dependent on the prepartum rise in fetal cortisol as occurs in other species.     

Compensatory changes in enzymes of arginine metabolism during renal hypertrophy in mice

The present study investigates enzyme activities of the urea cycle, transamidinase and ornithine–proline inter-conversion in the hypertrophied kidney after unilateral nephrectomy in mice. Surgical removal of the left kidney in mice led to compensatory enlargement of the right kidney after 1 and 14 days. This renal growth was associated with an increase in glomerular volume (but not number) and enlargement of the proximal convoluted tubules. The total renal protein content increased in proportion to the increase in kidney weight, but the protein per gram weight of kidney did not change. The specific activity of only ornithine aminotransferase (OAT), the rate-limiting enzyme in the conversion of ornithine to proline, increased in 2 weeks of hypertrophy. The specific activity of all other enzymes was unchanged. However, the total enzyme activity per kidney of all the enzymes, without exception, was elevated in the hypertrophied kidney. While the increase in total OAT activity was much more than the increase in kidney weight, all other enzymes increased more or less in proportion to the increase in renal mass. The results suggest that compensation in OAT activity to chronic reduction in renal mass was complete, but only partial in the case of other enzymes.     

Regulated Nuclear Trafficking of rpL10A Mediated by NIK1 Represents a Defense Strategy of Plant Cells against Virus

The NSP-interacting kinase (NIK) receptor-mediated defense pathway has been identified recently as a virulence target of the geminivirus nuclear shuttle protein (NSP). However, the NIK1–NSP interaction does not fit into the elicitor–receptor model of resistance, and hence the molecular mechanism that links this antiviral response to receptor activation remains obscure. Here, we identified a ribosomal protein, rpL10A, as a specific partner and substrate of NIK1 that functions as an immediate downstream effector of NIK1-mediated response. Phosphorylation of cytosolic rpL10A by NIK1 redirects the protein to the nucleus where it may act to modulate viral infection. While ectopic expression of normal NIK1 or a hyperactive NIK1 mutant promotes the accumulation of phosphorylated rpL10A within the nuclei, an inactive NIK1 mutant fails to redirect the protein to the nuclei of co-transfected cells. Likewise, a mutant rpL10A defective for NIK1 phosphorylation is not redirected to the nucleus. Furthermore, loss of rpL10A function enhances susceptibility to geminivirus infection, resembling the phenotype of nik1 null alleles. We also provide evidence that geminivirus infection directly interferes with NIK1-mediated nuclear relocalization of rpL10A as a counterdefensive measure. However, the NIK1-mediated defense signaling neither activates RNA silencing nor promotes a hypersensitive response but inhibits plant growth and development. Although the virulence function of the particular geminivirus NSP studied here overcomes this layer of defense in Arabidopsis, the NIK1-mediated signaling response may be involved in restricting the host range of other viruses.     

Enhancing effect of rasagiline on superoxide dismutase and catalase activities in the dopaminergic system in the rat

Rasagiline [N-propargyl-l(R)-aminoindan] is a selective irreversible MAO-B inhibitor as is (-)deprenyl. The effect of the drug on antioxidant enzyme activities on dopaminergic tissue was examined in male F-344 rats (8.5-months-old). Two experimental groups were infused subcutaneously with rasagiline saline solutions by means of osmotic minipumps implanted subcutaneously in the back of the rats. Control animals were also similarly implanted with saline filled mini-pumps. Three-and-one-half weeks later, animals were sacrificed and selected tissue samples removed from brain, kidney and heart. Two doses of rasagiline (0.5 mg/kg/day, 1.0 mg/kg/day, both for 3.5 weeks) significantly increased catalase activities about 2-fold in substantia nigra and striatum but not in hippocampus. Interestingly, in both renal cortex and medulla. catalase (CAT) activities were significantly increased. Both Mn- and Cu,Zn-superoxide dismutase (SOD) activities were increased 2 to 4 fold in substantia nigra, striatum and renal cortex and heart. Several groups, including our own have reported an extension of survival of deprenyl-treated animals of different species. Although the mechanism(s) of the life extension by deprenyl remains unresolved, it would be interesting to investigate the effect of rasagiline on the survival of animals, since deprenyl also was shown to increase antioxidant enzyme activities in brain dopaminergic regions.     

Diabetes related knowledge among residents and nurses: a multicenter study in Karachi,Pakistan

The existence of unilateral adrenal hyperplasia (AH) has been considered a rare cause of primary hyperaldosteronism (PA). In a prospective study we screened for PA in a non-selected (NSP) and selected hypertensive population (SP), to define the cause of PA. We included 353 consecutive patients with hypertension; age 20 to 88 years, 165 women and 188 men, from a university-based Hypertension and Nephrology Outpatient clinics (123 SP) and two primary care centres, (230 NSP) from the same catch-up area. Serum aldosterone and plasma renin activity (PRA) were measured and the ARR calculated. Verifying diagnostic procedure was performed in patients with both elevated aldosterone and ARR. Patients diagnosed with PA were invited for adrenal venous sampling (AVS) and offered laparoscopic adrenalectomy when AVS found the disease to be unilateral. After screening, 46 patients, 13% of the whole population (22.8% SP and 7.8% NSP) had aldosterone and ARR above the locally defined cut-off limits (0.43 nmol/l and 1.28 respectively). After diagnostic verification, 20 patients (6%) had PA, (14.5% SP and 1.4% NSP). Imaging diagnostic procedures with CT-scans and scintigraphy were inconclusive. AVS, performed in 15 patients verified bilateral disease in 4 and unilateral in 10 patients. One AVS failed. After laparoscopic adrenalectomy, 4 patients were found to have adenoma and 5 unilateral AH. One patient denied operation. The prevalence of PA was in agreement with previous studies. The study finds unilateral PA common and unilateral AH as half of those cases. As may be suspected PA is found in much higher frequency in specialised hypertensive units compared to primary care centers. AVS was mandatory in diagnosis of unilateral PA.     

Unilateral adrenal hyperplasia is a usual cause of primary hyperaldosteronism. Results from a Swedish screening study

ABSTRACT: BACKGROUND: The existence of unilateral adrenal hyperplasia (AH) has been considered a rare cause of primary hyperaldosteronism (PA). METHODS: In a prospective study we screened for PA in a non-selected (NSP) and selected hypertensive population (SP), to define the cause of PA. We included 353 consecutive patients with hypertension; age 20 to 88 years, 165 women and 188 men, from a university-based Hypertension and Nephrology Outpatient clinics (123 SP) and two primary care centres, (230 NSP) from the same catch-up area. Serum aldosterone and plasma renin activity (PRA) were measured and the ARR calculated. Verifying diagnostic procedure was performed in patients with both elevated aldosterone and ARR. Patients diagnosed with PA were invited for adrenal venous sampling (AVS) and offered laparoscopic adrenalectomy when AVS found the disease to be unilateral. RESULTS: After screening, 46 patients, 13% of the whole population (22.8% SP and 7.8% NSP) had aldosterone and ARR above the locally defined cut-off limits (0.43 nmol/l and 1.28 respectively). After diagnostic verification, 20 patients (6%) had PA, (14.5% SP and 1.4% NSP). Imaging diagnostic procedures with CT-scans and scintigraphy were inconclusive. AVS, performed in 15 patients verified bilateral disease in 4 and unilateral in 10 patients. One AVS failed. After laparoscopic adrenalectomy, 4 patients were found to have adenoma and 5 unilateral AH. One patient denied operation. CONCLUSION: The prevalence of PA was in agreement with previous studies. The study finds unilateral PA common and unilateral AH as half of those cases. As may be suspected PA is found in much higher frequency in specialised hypertensive units compared to primary care centers. AVS was mandatory in diagnosis of unilateral PA.     

Protection from radiation nephropathy by WR-2721

The efficacy of WR-2721 pretreatment against radiation injury to the growing kidney was evaluated in the weanling mouse. Immediately following unilateral nephrectomy, animals received intraperitoneal injections of saline or WR-2721 (220 mg/kg). Thirty minutes later both nonprotected (saline-treated) control animals and protected (WR-2721-treated) animals received 1000-rad single-fraction radiation to the remaining kidney. Other animals received WR-2721 immediately following unilateral nephrectomy but no radiation. Animals were sacrificed at 3 and 24 weeks. Nonirradiated animals treated with WR-2721 only showed normal compensatory renal growth, body growth, and renal function at 24 weeks. The nonprotected, irradiated animals exhibited renal growth inhibition without body growth inhibition, and renal functional abnormalities including elevation of serum BUN and reduction of glomerular filtration rate. Pretreatment with WR-2721 prior to 1000 rad prevented the renal growth inhibition and functional abnormalities seen in the nonprotected irradiated animals. Within the observation period there were no differences in renal morphology by light and electron microscopy between protected and nonprotected groups; only mild glomerular and tubular abnormalities compatible with radiation injury were seen. WR-2721 can modulate renal radiation injury; however, the growth and functional protection is not well correlated with specific histologic change. The dose reduction factor for WR-2721 renal growth protection is between 1.16 and 1.2. WR-2721 may have future clinical utility by increasing radiation tolerance of the kidney.     

Effect of cadmium on pulmonary and renal microsomal drug metabolizing enzymes of the guinea-pig

1. The effect of acute cadmium (Cd) treatment on pulmonary and renal microsomal aniline 4-hydroxylase and ethylmorphine N-demethylase enzyme activities of adult male guinea-pigs were assessed 72 hr following a single dose of Cd ion (2 mg Cd2+/kg i.p.). Tissue and microsomal Cd levels were also determined. 2. There were no significant differences between either lung or kidney tissue weights, microsomal protein contents or enzyme activities of Cd treated and control animals. 3. The tissues and microsomes of Cd-treated animals were found to have significantly higher levels of Cd than those of control animals. In Cd treated animals, tissue and microsomal Cd levels of kidney were found to be higher than that of lung. 4. In vitro addition of cadmium chloride (CdCl2) to incubation mixtures produced concentration related inhibitions of microsomal drug metabolizing enzymes in each tissue. However, in vitro effect of CdCl2 was found to be stronger on drug metabolizing enzymes of kidney than those of lung. In addition, while the strength of Cd effect was more pronounced on the activity of ethylmorphine N-demethylase than that of aniline 4-hydroxylase in the lung, the opposite was observed in the kidney.     

Aldehyde Dehydrogenase 1 Identifies Cells with Cancer Stem Cell-Like Properties in a Human Renal Cell Carcinoma Cell Line

Cancer stem cells (CSC) or cancer stem cell-like cells (CSC-LCs) have been identified in many malignant tumors. CSCs are proposed to be related with drug resistance, tumor recurrence, and metastasis and are considered as a new target for cancer treatment; however, there are only a few reports on CSCs or CSC-LCs in renal cell carcinoma (RCC). Different approaches have been reported for CSC identification, but there are no universal markers for CSC. We used two different approaches, the traditional side population (SP) approach, and the enzymatic (aldehyde dehydrogenase 1 (ALDH1)) approach to identify CSC-LC population in two RCC cell lines, ACHN and KRC/Y. We found that ACHN and KRC/Y contain 1.4% and 1.7% SP cells, respectively. ACHN SP cells showed a higher sphere forming ability, drug resistance, and a slightly higher tumorigenic ability in NOD/SCID mice than Non-SP (NSP) cells, suggesting that cells with CSC-LC properties are included in ACHN SP cells. KRC/Y SP and NSP cells showed no difference in such properties. ALDH1 activity analysis revealed that ACHN SP cells expressed a higher level of activity than NSP cells (SP vs. NSP: 32.7% vs 14.6%). Analysis of ALDH1-positive ACHN cells revealed that they have a higher sphere forming ability, self-renewal ability, tumorigenicity and express higher mRNA levels of CSC-LC property-related genes (e.g., ABC transporter genes, self-replication genes, anti-apoptosis genes, and so forth) than ALDH1-negative cells. Drug treatment or exposure to hypoxic condition induced a 2- to 3-fold increase in number of ALDH1-positive cells. In conclusion, the results suggest that the ALDH1-positive cell population rather than SP cells show CSC-LC properties in a RCC cell line, ACHN.     

Analysis of a temperature-sensitive mutant rotavirus indicates that NSP2 octamers are the functional form of the protein

Evidence that NSP2 plays a role in packaging and replication comes from studies on tsE(1400), a rotavirus mutant with a temperature-sensitive (ts) lesion in the NSP2 gene. Cells infected with tsE and maintained at nonpermissive temperature contain few replication-assembly factories (viroplasms) or replication intermediates and produce virus particles that are mostly empty. Sequence analysis has indicated that an A152V mutation in NSP2 is responsible for the ts phenotype of tsE. To gain insight into the effect of the mutation on the octameric structure and biochemical activities of tsE NSP2, the protein was expressed in bacteria and purified to homogeneity. Analytical ultracentrifugation showed that tsE NSP2 formed octamers which, like those formed by wild-type (wt) NSP2, undergo conformational change into more compact structures upon binding of nucleotides. However, exposure to Mg(2+) and the nonpermissive temperature caused disruption of the tsE octamers and yielded the formation of polydisperse NSP2 aggregates, events not observed with wt octamers. Biochemical analysis showed that the RNA-binding, helix-destabilizing and NTPase activities of tsE NSP2 were significantly less at the nonpermissive temperature than at the permissive temperature. In contrast, these activities for wt NSP2 were higher at the nonpermissive temperature. Our results indicate that the octamer is the fully functional form of NSP2 and the form required for productive virus replication. The propensity of tsE NSP2 to form large aggregates provides a possible explanation for the inability of the protein to support packaging and/or replication in the infected cell at the nonpermissive temperature.     

Ghrelin Acts as an Antioxidant Agent in the Rat Kidney

Ghrelin has recently been shown to improve renal function in rat with acute renal failure. In this setting, the protective effects have been suggested to be due to its antioxidant properties. Thus, the aim of this study was to measure the antioxidant abilities of this hormone via enzymatic and lipid peroxidation analyses. Wistar rats were divided into two control and two treatment groups, the treated animals receiving 3 nmol of ghrelin as subcutaneous administrations on each of 10 consecutive days and physiological saline injected to controls. Catalase (CAT) activity was significantly higher in the treated animals when compared to controls, while in contrast, lipid peroxidation measured by thiobarbituric acid reactive substances (TBARS), was significantly reduced in the ghrelin treated animals. Furthermore, superoxide dismutase (SOD) activity and glutathione (GSH) content were both much higher in treated female rats than in controls and although there was a slight increase in glutathione peroxidase (GPx) activity in kidneys of ghrelin treated rats, the difference was insignificant. These findings suggest that ghrelin has beneficial antioxidant properties in the rat kidney by increasing antioxidant enzyme activities. These effects were more noticeable in treated female rats, possibly due to higher levels of estrogen.     

Lowered plasma erythropoietin in hypoxic rats with kidney tubule lesions

The role of the kidney tubules in the renal formation of erythropoietin is incompletely understood. Therefore, the capability to produce erythropoietin in response to hypoxia was studied in rats with tubular lesions. Nephron damage was induced in two different ways. First, rats were treated with the nephrotoxic aminoglycoside gentamicin (67.5 mg/kg and day) for 14 days. The animals were then subjected to simulated altitude (6,800 m) for 6 h. The resulting plasma erythropoietin concentration was significantly lower (0.5 IU/ml) than in saline treated control rats exposed to hypoxia (1.0 IU/ml). Second, unilateral hydronephrosis was induced by ureteral ligation. The contralateral kidney was removed immediately before the animals were exposed to simulated altitude for 6 h. The plasma erythropoietin concentration in the ureter-ligated rats did not increase above the value (0.3 IU/ml) in hypoxia exposed anephric rats. These results indicate that the production of erythropoietin is reduced following tubular injury. Tubule cells may directly produce the hormone or interfere with the O2-sensing mechanisms controlling its synthesis. The latter hypothesis would seem to be supported by our failure to demonstrate in vitro erythropoietin production by the two established kidney tubule cell lines, LLC-PK1 and PK-15.     

Oxidative stress parameters in blood, liver, and kidney of diabetic rats treated with curcumin and/or insulin

This study evaluated the effects of curcumin and/or insulin on antioxidant enzyme activity in blood, liver, and kidney, as well as on lipid peroxidation and delta aminolevulinic dehydratase (δ-ALA-D) activity, and a histopathological analysis of streptozotocin-induced diabetic rats. The animals were divided into six groups (n = 6): control/saline (C); control/curcumin (CCur); diabetic/saline (D); diabetic/insulin (DIns); diabetic/curcumin (DCur); and diabetic/insulin/curcumin (DInsCur). After 30 days of treatment with curcumin and/or insulin, the animals were sacrificed and the liver, kidney, and serum were used for experimental determinations. Results of histopathological analysis showed that the treatment with insulin ameliorate renal and hepatic lesions from both DIns and DInsCur groups. TBARS levels were significantly increased in serum, liver, and kidney in D group and the administration of curcumin and insulin prevented this increase in DIns and DCur groups. The activities of catalase (CAT), superoxide dismutase, and δ-ALA-D presented a significant decrease in the liver and kidney D group when compared to C group (P < 0.05). The animals treated with curcumin and insulin presented an increase of CAT activity, revealing a positive interaction between both substances. The treatments with curcumin or insulin prevented oxidative stress in blood, through modulation of enzymatic antioxidant defenses. These findings contributed to the comprehension that antioxidants from medicinal plants could be used as adjuvant in the treatment of this endocrinopathy and not as single therapy.     

Underfeeding and exposure to short photoperiod alters rat pineal and Harderian gland lysosomal enzyme activities

Harderian gland (HG) weight and lysosomal enzyme activity were evaluated after 21-day-old female rats were singly caged in a long (LP; 14:10 LD) or short (SP; 8:16 LD) photoperiod and fed on one of two dietary regimens (fed ad libitum or 50% underfed) for 50 days; an additional fed and an underfed group of animals in LP were injected every afternoon with 100 micrograms melatonin. Absolute HG weights were significantly lower in all underfed groups compared to their respective fed controls or to the LP fed control group. Absolute HG weights of underfed rats in SP were significantly lower than the underfed rats in LP. Relative HG weights (mg/100 g body wt) were significantly higher in the underfed saline or melatonin-treated groups compared to their respective fed controls; however, HG of the underfed SP group were not different from SP-fed controls. No significant differences in HG acid phosphatase, hexosaminidase, and beta-glucuronidase activities were observed in any of the treatment groups maintained in LP. Acid phosphatase, hexosaminidase, and beta-glucuronidase activities were significantly elevated in HG of underfed animals maintained in SP compared to their respective fed controls or to the LP-underfed group. Both the underfed control and the underfed-melatonin treated groups had lower pineal protein values than their respective fed groups; underfed animals in 8:16 LD had similar pineal protein values compared to those of the fed control group in SP. Significant effects of photoperiod and underfeeding with no interaction between these variables were observed on pineal acid phosphatase. The fed group maintained in 8:16 LD had significantly higher acid phosphatase activity than the fed group kept in 14:10 LD. In conclusion, underfeeding resulted in severely reduced body weights and absolute Harderian gland weights. Increased activity in certain lysosomal enzymes occurred in both the pineal and Harderian gland and in some instances this was dependent upon the light cycle and dietary regimen to which the animals were exposed.     

The nonstructural glycoprotein of rotavirus affects intracellular calcium levels.

Rotavirus infection of monkey kidney cells has been reported to result in a significant increase in the concentration of intracellular calcium. This increase in intracellular calcium was associated with viral protein synthesis and cytopathic effects in infected cells. We tested the effect of individual rotavirus proteins on intracellular calcium concentrations in insect Spodoptera frugiperda (Sf9) cells. Insect cells were infected with wild-type baculovirus or baculovirus recombinants that contained an individual rotavirus gene. The cells were harvested at different times postinfection, and the intracellular calcium concentration was measured by using fura-2 as a fluorescent calcium indicator. We found that the concentration of intracellular calcium was increased nearly fivefold in infected Sf9 cells that expressed the nonstructural glycoprotein (NSP4) of group A rotavirus, and this increase in intracellular calcium concentration coincided with NSP4 expression. A similar result was observed in insect cells expressing NSP4 from a group B rotavirus, suggesting the conservation of this function among rotavirus groups. Expression of the other 10 rotavirus proteins or of wild-type baculovirus proteins in Sf9 cells did not significantly increase intracellular calcium levels. These results suggest that the nonstructural glycoprotein NSP4 is responsible for the increase in cytosolic calcium observed in rotavirus-infected cells.     

Reinvestigation of denervation diuresis and natriuresis in conscious dogs.

The function of innervated and denervated kidney was compared in clearance studies with conscious dogs. The animals were prepared for experiments by unilateral renal denervation and surgical division of the bladder to form two hemibladders enabling separate urine collection from two kidneys. The mean urine flow was 6% higher for the denervated kidney (not significant) while mean differences for osmolar clearance (+ 13%), sodium excretion (+21%) and GFT (+5%) were all significant (P less than 0.05). When corrected to 100 ml GFR, sodium excretion was not significantly higher for the denervated kidney. In most experiments higher sodium excretion on the denefvated side was associated with higher GFR. Thus, contrary to some earlier views, a slight increase in the excretory function which follows denervation of the kidney is demonstrable also in conscious undisturbed animals. The data suggest that increased haemodynamics of the denervated kidney are responsible for higher excretion, but do not exclude a contribution of inhibited tubular reabsorption.     

Effect of felodipine on renal hemodynamics and excretion in the dog

The effects of felodipine on renal hemodynamics and excretion were evaluated in the anesthetized dog. Unilateral renal arterial infusion of felodipine produced ipsilateral increases in the absolute and fractional excretion of sodium and water which were greater than those of potassium; these effects occurred in the absence of changes in mean arterial pressure, renal blood flow, or glomerular filtration rate. There were no significant effects on renal hemodynamic or excretory function in the contralateral kidney. The unilateral renal arterial infusion of isotonic saline or vehicle produced no significant effects on renal hemodynamic or excretory function in either ipsilateral or contralateral kidney. Felodipine, a calcium antagonist with vasodilator antihypertensive properties, in doses which do not affect systemic or renal hemodynamics in the dog, increased urinary flow rate and sodium excretion by decreasing renal tubular water and sodium reabsorption. As a vasodilator antihypertensive agent, felodipine possesses potentially advantageous diuretic and natriuretic properties.     

Recombinant Destabilase-Lysozyme: Synthesis de novo in E. coli and Action Mechanism of the Enzyme Expressed in Spodoptera frugiperda

Destabilase-lysozyme (DL) from salivary gland secretion of the medicinal leech (Hirudo medicinalis) is as a member of the invertebrate lysozyme family, which sharply differs from other lysozyme families. In this study, DL lysozyme function was confirmed during expression of a gene encoding DL in Escherichia coli. Several constructs of the expression vectors pKK OmpA and pET-3A with or without bacterial, leech, or yeast signal peptides (SP) were used. The use of a construct without signal peptide genes resulted in normal growth of the transformed cells. Transformation of E. coli cells with the constructs containing SP was accompanied by the disruption of the forming cells. The use of the expression vector pET-32 LTC-System for production of DL as a fusion protein with thioredoxin also resulted in normal cell growth. However, specific activity of DL isolated from such cells was significantly lower than that of enzyme purified from extracts of Spodoptera frugiperda cells, which were infected with the baculovirus vector carrying DL cDNA. It is shown that the action mechanism of invertebrate lysozyme does not differ from that of other families: recombinant DL from S. frugiperda extracts catalyzed cleavage of synthetic substrate, hexamer of N-acetylglucosamine, to di- and tetramers, which is typical for enzymatic function of other lysozyme families.     

Susceptibility of rainbow trout Oncorhynchus mykiss,Atlantic salmon Salmo salar and coho salmon Oncorhynchus kisutch to experimental infection with sea lice Lepeophtheirus salmonis

Physiological, immunological and biochemical parameters of blood and mucus, as well as skin histology, were compared in 3 salmonid species (rainbow trout Oncorhynchus mykiss, Atlantic salmon Salmo salar and coho salmon O. kisutch) following experimental infection with sea lice Lepeophtheirus salmonis. The 3 salmonid species were cohabited in order to standardize initial infection conditions. Lice density was significantly reduced on coho salmon within 7 to 14 d, while lice persisted in higher numbers on rainbow trout and Atlantic salmon. Lice matured more slowly on coho salmon than on the other 2 species, and maturation was slightly slower on rainbow trout than on Atlantic salmon. Head kidney macrophages from infected Atlantic salmon had diminished respiratory burst and phagocytic capacity at 14 and 21 d post-infection (dpi), while infected rainbow trout macrophages had reduced respiratory burst and phagocytic capacities at 21 dpi, compared to controls. The slower development of lice, coupled with delayed suppression of immune parameters, suggests that rainbow trout are slightly more resistant to lice than Atlantic salmon. Infected rainbow trout and Atlantic salmon showed increases in mucus lysozyme activities at 1 dpi, which decreased over the rest of the study. Mucus lysozyme activities of infected rainbow trout, however, remained higher than controls over the entire period. Coho salmon lysozyme activities did not increase in infected fish until 21 dpi. Mucus alkaline phosphatase levels were also higher in infected Atlantic salmon compared to controls at 3 and 21 dpi. Low molecular weight (LMW) proteases increased in infected rainbow trout and Atlantic salmon between 14 and 21 dpi. Histological analysis of the outer epithelium revealed mucus cell hypertrophy in rainbow trout and Atlantic salmon following infection. Plasma cortisol, glucose, electrolyte and protein concentrations and hematocrit all remained within physiological limits for each species, with no differences occurring between infected and control fish. Our results demonstrate that significant differences in mucus biochemistry and numbers of L. salmonis occur between these species.