Lipoprotein lipase (LPL, E.C. 3.3.1.34) is the enzyme responsible for hydrolysis of triacylglycerols in plasma lipoproteins, making the fatty acids available for use by subjacent tissues. LPL is functional at the surface of endothelial cells, but it is not clear which cells synthesize the enzyme and what its distribution is within tissues and vessels. We have searched for specific cell expression of the LPL gene by in situ hybridization using a RNA probe and for the corresponding protein distribution by immunocytochemistry on cryosections of some LPL-producing tissues of guinea pigs. In white and brown adipose tissues, heart and skeletal muscle, and lactating mammary gland, there was positive hybridization for LPL mRNA over all members of the major cell types, indicating that mature and immature adipocytes, muscle cells, and mammary epithelial cells are main sources of LPL. In large vessels, LPL expression was detected in some smooth muscle cells in the media layer. There was no positive hybridization for LPL mRNA over endothelial cells in any of the tissues studied, but there was immunoreaction for LPL protein at endothelial surfaces of all blood vessels. In the kidney, there was strong immunofluorescence at the vascular endothelium, particularly in the glomeruli, but little or no LPL mRNA was detected in the surrounding cells. These observations suggest that in some tissues LPL is synthesized by parenchymal cells and spreads along the vascular mesh. Transfer to the vascular endothelium is, however, not the only route taken by LPL. In the mammary gland most of the enzyme protein appeared to be secreted, partly in association with milk fat droplets.(ABSTRACT TRUNCATED AT 250 WORDS)

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Sensitivity o f eggs and sac fry of the com mon carp {Cyprinus carpio) to pH levels in th e range o f 4.5 to 7.5 was assessed up to 117 h after fertilization. Studied param eters were rate o f em bryonic development, time and duration of hatching, and spinal cord deformation. In the pH range between 4.75 and 5.2 egg mortality was highest and a delay in the rate o f embryonic development and hatching was observed in the surviving embryos. A strong increase of spinal cord deform ation o f sac fry occurred in the lo w er pH ranges (pH 5.5-4.75). Common carp appeared to be more sensitive to acid stress than m an y other species of fish.

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All these results suggest that maternal malnutrition is not primarily responsible for the impaired intestinal maturation in rat fetuses from alcohol-treated mothers; indirect effects of ethanol and/or its derivatives throughout embryo-fetal development could be necessary to promote this intestinal delay.