Cattle, retina

The rod pigment rhodopsin is readily available from cattle retinas and has been studied for many... 

NEOBIOSYNTHESIS OF PHOSPHATIDYLINOSITOL AND OF OTHER GLYCEROLIPIDS IN THE ENTIRE CATTLE RETINA... 

At early incubation times PA synthesis was the higher both in toad and cattle retina however, a remarkable time-dependent increase in the incorporation of the precursor in triacylglycerol was found. After 90 min of incubation the labeling of the neutral glyceride surpassed that of all other lipid classes (Giusto Bazan,... 

Table 1. Time course of specific activities in cattle retina gly-cerides using C-glycerol as precursor...

Toad (Bufo arenarum, Hensel) brains and retinas were excised immediately after decapitation. Cattle eyes obtained from a local slaughterhouse were kept within crushed ice and used within 2 hours. Cattle and toad retinas were incubated at 37 and 23 C respectively under 5% CO2 in oxygen in the medium of Ames Hastings (1956) containing 2 mg/ml glucose. 5 yCi per cattle retina (or per 17 toad retinas) of both u- C -glycerol (8.75 mCi/mmol) and 5,6,8,9,11,12, 14,15- h -free arachidonic acid (80 Ci/mmol) from New England Nuclear were added to the media. 

Large quantities of docosahexaenoate are present in all retina glycerolipids, due to the contribution of lipids from the outer segments of photoreceptors, which are known to be enriched in this fatty acid. However, the same holds for diacylglycerols and phosphatidic acid, which likely are not concentrated in these structures. The unusual composition of these intermediates suggests that an important proportion of toad retinal lipid metabolism may be involved in supporting photoreceptor lipid composition. The concentration of both DG and PA is 4-5 fold higher in the toad than in the cattle retina (Aveldaho Bazan, 1974 and unpublished). 

Table 1. Fatty acid composition of cattle retina glycerolipids.

In cattle retina diacylglycerols 18 0-20 4 predominate (Table 1) combination which does not appear in any of the lipids derived from... 

To inquire about the relations among some glycerolipids in the cattle retina we undertook a time-course study on the simultaneous uptake of C-glycerol and H-arachidonic acid. A comparison is made with the toad (Table 2). The specific activities of cattle retina lipids show a rapid labeling by glycerol of PA at 5 min incubation, followed by a steadily increasing accumulation of label in the other lipids, particularly diacyl- and triacylglycerols. 

The distribution of radioactivity among retina lipids after 30 min incubation shows that in the toad retina the preferred flow of glycerol is towards PI, whereas arachidonate gets predominantly into PE (Table 3). By the contrary, the label from both precursors in cattle retina lipids is similarly distributed. 

EFFECTS OF DIVALENT CATIONS, K+, AND X-537A ON GLYCEROLIPID METABOLISM IN THE CATTLE RETINA... 

When cattle retinas are incubated in an ionic medium that resembles cerebrospinal fluid in its electrolyte composition (Ames Hastings, 1956 Ames Gurian, 1963) a heightened rate of C-gly-cerol flux towards triacylglycerol is disclosed (Bazan et al.,... 

Cattle retinas brought to the laboratory in light-tight containers packed within crushed ice were used no later than three hours after slaughter. In all cases a preincubation of 10 min was followed by the addition of 5 yCi of (U- C)glycerol per retina. 

Table 2. Effects of varying the divalent cations concentration on cattle retina lipids labeling by C-glycerol...

Next, we decided to observe the effect of varying calcium concentrations on the C-glycerol uptake. The labeling of total phospholipids increased in a Ca concentration - dependent fashion in agreement with a similar observation made in our laboratory using cattle retina (Giusto Bazan, 1977). Again phosphatidic acid... 

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