Perfluorochemical (PFC) liquids are biologically inert and nonbiotransformable substances that, when used as breathing medium, may be transported across the lung epithelium in small quantities, distributed throughout the body, and ultimately vapourized through the lungs and transpired through the skin. To further evaluate the uptake, biodistribution and elimination of a PFC liquid (perfluorodecalin) in the neonatal population, arterial blood, tissue and expired gas samples were obtained from preterm lambs (105-114 days gestation). Two groups of premature lambs were studied: Group I (n = 4) lambs were liquid ventilated from birth for 1 h and killed without exposure to gas ventilation (GV) and Group II (n = 5) lambs were liquid ventilated for 1 h followed by up to 2 h of GV. Samples were analysed by electron-capture gas chromatography and data were expressed in nl of PFC/ml of blood or gas and nl of PFC/gm tissue. During liquid ventilation and subsequent GV, PFC blood levels significantly increased (P < 0.001) from baseline control levels (0.007 +/- 0.001 SE nl PFC/ml blood) to a high of 2.95 +/- 1.03 SE nl PFC/ml blood. Perfluorochemical levels measured in expired gas (Group II) demonstrated a rapid decrease as a function of time of GV. Tissue levels of PFC indicated that uptake of PFC in Group I was significantly different (P < 0.001) than baseline levels and organ dependent; the highest levels were in the lungs (221 +/- 26.2 SE nl PFC/g tissue) and the lowest in the liver (2.24 +/- 1.6 SE nl PFC/g tissue). Comparison of tissue levels of PFC between groups indicated a 34.8% mean decrease across organs in Group II compared with Group I. These data indicate that PFC uptake and elimination is organ dependent and that PFC liquids can be eliminated through the lungs upon return to GV. Sustained PFC blood levels may be related to residual PFC in the organs and lung as well as regional variation in ventilation-perfusion matching upon return to GV.

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Thirteen Targhee rams selected for rate and efficiency of gain for 4 yr (1.5 generations) were compared with 10 rams from a Targhee line with no selection for over 20 yr to determine if selection for these traits would be associated with changes in the secretion of growth hormone (GH), thyrotropin (TSH) and(or) prolactin (PRL). Selected rams exhibited greater birth weight, average daily gain (ADG) and feed consumed/day during a 6-wk individual feeding regimen, and exhibited greater overall ADG during a 16-wk feeding trial as compared with the unselected rams. Temporal blood plasma samples were collected at 15-min intervals for 8 h from each of the 23 rams for hormone analysis. Selected rams exhibited greater overall mean GH (6.1 +/- .4 vs 4.6 +/- .5 ng/ml), overall mean TSH (8.6 +/- 1.2 vs 6.2 +/- .7 ng/ml) and baseline mean TSH (8.0 +/- 1.1 vs 5.6 +/- .5 ng/ml) than the unselected rams. Although the adjusted GH spike amplitude value was higher in the selected line (12.1 +/- 3.0 vs 7.4 +/- .8 ng/ml), this difference was not significant. No differences were observed with any of the variables of PRL secretion. In addition, there were no significant correlations between any of the hormone variables and any of the feed or gain data. These data support the hypothesis that Targhee rams selected for rate and efficiency of gain exhibit higher plasma levels of GH and TSH than unselected rams of the same breed.

The chemical nature and variations in serum concentrations of growth hormone binding protein (GHBP) from humans, rabbits, and rodents have been reported. To date little is known about the GHBP of domestic animals. Therefore, we initiated these studies to determine whether a serum GHBP was present in domestic animals and to purify the binding protein (BP) from serum of selected species. Using a dextran-coated charcoal separation assay, specific growth hormone (GH) binding was demonstrated in ovine, bovine, chicken, human, goose, porcine, and equine serum (listed in sequence from lowest to highest binding). Variation in BP activity was relatively high, both within and between species. Yearling ewes had higher serum GHBP than either prepubertal (4 mo) or older (5 yr) ewes. The GHBP was partially purified from chicken, ovine, and porcine serum using GH affinity chromatography. These BP had high affinity (Ka = 2 x 10(8) to 2 x 10(9) L/mol, depending on species) and low capacity (2 x 10(-10) to 5 x 10(-11) mol/unit of protein) for human GH but showed lower binding affinity for homologous GH (Ka = 2 x 10(7) L/mol). The porcine GHBP had the highest and ovine GHBP the lowest affinity for human GH. Other heterologous somatotropic hormones, ovine placental lactogen, and ovine GH displayed higher binding affinity to chicken and pig BP than the respective homologous hormones. Further chromatographic purification of the porcine GHBP resulted in an additional 1,000-fold purification. The estimated molecular weight of porcine GHBP is 50,000 to 60,000 Da. These results demonstrate that the serum from all domestic species tested contains a specific GH-binding moiety and that under the conditions described here human GH is a more efficient ligand than the homologous hormone.