The release and vascular action of bradykinin in the isolated perfused bovine udder

Systemic and mammary gland disposition of enrofloxacin in healthy sheep following intramammary administration

Background

Mastitis is one of the most important diseases affecting dairy sheep. Antimicrobial drugs are often administered directly through teat to treat or prevent this disease, but data on drug distribution within glandular tissue are scarce and it cannot be estimated from concentrations in milk. Thus, the aim of this study was to investigate systemic and mammary gland distribution of enrofloxacin after intramammary administration. The drug was administered to 6 healthy lactating Assaf sheep with an injector containing an enrofloxacin preparation (1 g drug/5 g ointment). Blood samples were collected at 0, 30, 60, 90, 120, 150 and 180 min. Animals were then sedated and sacrificed, and glandular tissue samples were obtained from treated udders at 2, 4, 6 and 8 cm height. Enrofloxacin concentrations were measured in plasma and tissue samples by UV high-performed liquid chromatography.

Results

Mean enrofloxacin plasma concentrations were below 0.5 μg/mL. Mean tissue concentrations decreased in mammary gland with vertical distance from the teat, ranging from 356.6 μg/g at 2 cm to 95.60 μg/g at the base of the udder. Glandular tissue concentrations best fitted to a decreasing monoexponential model, and showed a good correlation with an ex vivo model previously developed.

Conclusions

Enrofloxacin concentrations were effective in the entire glandular tissue against the main pathogens causing mastitis in sheep. These results suggest that this drug may be suitable to treat mastitis in sheep by intramammary administration.

Udder edema and association with some serum biochemical measurands and dietary factors in first calving cows

The aims of this study were to determine some major biochemical alterations observed in first calving cows with udder edema during the periparturient period and to detect some associations between dietary factors and the disease. For that, the concentrations of some electrolytes (Na(+), K(+), Cl, Ca(2+), P and Mg(2+)), lipid (triglycerides and cholesterol) markers and lipoproteins (HDL, LDL and VLDL) and total proteins were measured in serum samples collected from 70 first calving cows (35 with udder edema and 35 healthy ones) whereas the percentages of dry matter and crude proteins and the electrolyte (Na(+), K(+), Cl, Ca(2+), Mg(2+), P and sulphates) amounts in feed rations were determined in parallel. The total protein, the calcium and the phosphorus as well as the concentrations of lipid markers and lipoproteins (HDL and LDL) were significantly decreased in first calving cows with udder edema compared to the healthy ones and these biochemical alterations were correlated with a reduced dry matter content and an electrolyte desequilibrium mainly involving Na(+) and Cl(-) in feed rations distributed to the cows with udder edema. To our knowledge the mechanism(s) of physiologic udder edema is uncertain and the obtained results suggest that a transient liver dysfunction (decreased total protein and LDL) probably linked to a feed ration deficient in dry matter may be involved in the aetiology of the udder edema in first calving cows.

Tissue distribution of enrofloxacin after intramammary or simulated systemic administration in isolated perfused sheep udders

OBJECTIVE

To determine the tissue distribution of enrofloxacin after intramammary or simulated systemic administration in isolated perfused sheep udders by measuring its concentration at various sample collection sites.

SAMPLE

26 udders (obtained following euthanasia) from 26 healthy lactating sheep.

PROCEDURES

For each isolated udder, 1 mammary gland was perfused with warmed, gassed Tyrode solution. Enrofloxacin (1 g of enrofloxacin/5 g of ointment) was administered into the perfused gland via the intramammary route or systemically via the perfusion fluid (equivalent to a dose of 5 mg/kg). Samples of the perfusate were obtained every 30 minutes for 180 minutes; glandular tissue samples were obtained at 2, 4, 6, and 8 cm from the teat base after 180 minutes. The enrofloxacin content of the perfusate and tissue samples was analyzed via high-performance liquid chromatography with UV detection.

RESULTS

After intramammary administration, maximun perfusate enrofloxacin concentration was detected at 180 minutes and, at this time, mean tissue enrofloxacin concentration was detected and mean tissue enrofloxacin concentration was 123.80, 54.48, 36.72, and 26.42 μg/g of tissue at 2, 4, 6, and 8 cm from the teat base, respectively. Following systemic administration, perfusate enrofloxacin concentration decreased with time and, at 180 minutes, tissue enrofloxacin concentrations ranged from 40.38 to 35.58 μg/g of tissue.

CONCLUSIONS AND CLINICAL RELEVANCE

By 180 minutes after administration via the intramammary or systemic route in isolated perfused sheep mammary glands, mean tissue concentration of enrofloxacin was greater than the minimum inhibitory concentration required to inhibit growth of 90% of many common mastitis pathogens in sheep. Use of either route of administration (or in combination) appears suitable for the treatment of acute mastitis in sheep.

Peptide hormone regulation of angiogenesis

It is now apparent that regulation of blood vessel growth contributes to the classical actions of hormones on development, growth, and reproduction. Endothelial cells are ideally positioned to respond to hormones, which act in concert with locally produced chemical mediators to regulate their growth, motility, function, and survival. Hormones affect angiogenesis either directly through actions on endothelial cells or indirectly by regulating proangiogenic factors like vascular endothelial growth factor. Importantly, the local microenvironment of endothelial cells can determine the outcome of hormone action on angiogenesis. Members of the growth hormone/prolactin/placental lactogen, the renin-angiotensin, and the kallikrein-kinin systems that exert stimulatory effects on angiogenesis can acquire antiangiogenic properties after undergoing proteolytic cleavage. In view of the opposing effects of hormonal fragments and precursor molecules, the regulation of the proteases responsible for specific protein cleavage represents an efficient mechanism for balancing angiogenesis. This review presents an overview of the actions on angiogenesis of the above-mentioned peptide hormonal families and addresses how specific proteolysis alters the final outcome of these actions in the context of health and disease.

Adrenergic receptors in the bovine mammary artery

The response of isolated preparations of bovine mammary artery was investigated, with the aim of characterising further the adrenergic receptor subtypes present. Noradrenaline (NA) and the alpha(1) agonist phenylephrine gave sigmoidal dose-response curves with pEC(50) values of 5.97+/-0.07 (N=34) and 6.21+/-0.32 (N=8), respectively. Stimulation of alpha(2) receptors with UK 14,304 produced a weak response with pEC(50) of 6.78+/-0.38 (N=7), and maximal contraction of 17.8+/-9.9% relative to NA. A61603, an alpha(1A) agonist, gave a curve parallel to NA, but shifted to the left (pEC(50) of 6.98+/-0.19 (N=5)); this drug had an increased potency of 10-fold relative to NA, and 4-fold relative to phenylephrine. Schild analysis of curves obtained with the alpha(1) antagonist prazosin gave a pA(2) of 8.70+/-0.47 (N=6-9), whereas the alpha(2) antagonist yohimbine resulted in a pA(2) of 7.65+/-0.16 (N=4). The alpha(1A) receptor antagonists WB4101 and 5-methylurapidil gave pA(2) values of 9.39+/-0.69 (N=4) and 7.72+/-0.02 (N=2-3), respectively. The irreversible alpha(1B) inhibitor CEC reduced the pEC(50) from 5.39+/-0.12 to 4.31+/-0.18 (N=7) only at the highest dose used, and high doses of the alpha(1D) antagonist BMY 7378 produced a shift to the right at giving a pA(2) of 7.37+/-0.08 (N=3). These results suggest major involvement of the alpha(1B) adrenergic receptor subtype in contraction of the bovine mammary artery, which is similar to the human internal mammary artery.