The Sterol Content In Scapharca Inaequivalvis
THE STEROL CONTENT IN SCAPHARCA INAEQUIVALVIS
OF THE BLACK SEA
R.P. Kandiuk
Odessa Branch Institute of biology of Southern Seas, National
Academy of Sciences of Ukraine
We take an interest in the bivalve mollusks in many reasons. Except of their commercial value (the food for man and some marine Crustacea), the special interest present the biological and pharmacological role of fat acids, containing in them (It is known that fat acid 20 : 5n3 can be useful in treatment of cardiovascular diseases).The sterols constituents of bivalve mollusks is also of biological and pharmacological interest. They are precursors of hormonally active substances and of group D3 vitamins and because of their hypocholesterolemic action on mammals and birds.
Scapharca attract our attention as autacclimatizant from Adriatic to Black Sea and as potential source of provitamins D3. Except of this, it is very important to investigate the influence of ecological conditions on quantitative content of sterols in S.inaequivalvis (Bruguiere).
It is very few known about sterol constituent in this mollusk. The data were obtained by investigators applied to sterols of Scapharca from Adriatic Sea. As to Piretti data (Piretti et al., 1982), the lipidic fractions, extracted from the S.inaequivalvis tissues, contain practically all sterols in the free state, while only traces of esterified sterols were identified. There are not at all data about sterols of Scapharca that appears in Black Sea from Adriatic shores. We have the first steps undertaken to cognize the sterols content of autacclimatisant S. inaequivalvis.
Samples were in august 1988 in Zhebriyanskaya bay and in august 1991 at Caucasian coast collected. There were three sizes of mollusk investigated: 2-3, 3-4 and 4-5 cm. The total amount of provitamins D3, 7- dehydrocholesterol, methasterol, lathosterol and cholesterol was determined by thin-layer chromatography (Lisboa, 1969), photocolorimetric (Moore and Baumann, 1952; Rzhavskaya, 1966) and spectrocolorimetric (Jahimovich et al., 1974) methods.
There are mosaic changes in sterols content in Scapharca of different sizes and inhabited in different ecological conditions. So, the total amount of provitamins D3 in mollusk from Zhebriyanskaya bay (% of insaponifiable fraction) was more than three times over in Scapharca of 3-4 cm compared to Scapharca of 2-3 cm (2,93% and 0,87% accordingly). The percentages content of identificated 7-dehydrocholesterol, lathosterol, methosterol and cholesterol were also much higher in Scapharca of 3-4 cm. Calculating on the wet weight only percentage content of lathosterol and methasterol was higher in mollusk of this size, while cholesterol, 7-dehydrocholesterol and total amount of provitamins D3 was higher in Scapharca of 2-3 cm size.
In august 1991 samples of Scapharca were collected at Caucasian coast. The total amount of provitamins D3 in Scapharca of 2-3 cm size was more than twice higher in mollusks from st.119, in region of N. Michailovka compared with that of st.143, region of Golovinka (2,07% and 0,99% accordingly), but the content of 7-dehydrocholesterol and cholesterol were higher on station 143 (0,46 and 0,03; 4,12 and 3,74 accordingly). The lathosterol was absent in Scapharca at this station at all.
Comparing two groups of Scapharca - 3-4 and 4-5 cm size it was discovered that the total amount of provitamin D3 practically was identical. Only the content of cholesterol was more than twice higher in Scapharca of 4-5 cm. On the ground of receiving data may come to conclusion that ecological conditions have more influence on content of sterols in Scapharca than size of mollusk.
The investigation of anatomical distribution of sterols in Scapharca is of great interest since it maybe useful of gaining information about a biological role of these lipid components. We have carried out such investigations on another mollusks. Scapharca from the Black Sea was not investigated in consequence of insufficient samples of mollusks. We are faced with solving of this problem. Such investigations were carried out by Italian scientists (Piretti et al., 1982) on Scapharca inaequivalvis collected on the Adriatic shores. To obtain the information about the anatomical distribution of sterols, the mollusks were dissected at gills, mantle, foot with digestive diverticula, haemolymph and analyzed separately. The samples were collected monthly (to verify if significant variations in the anatomical distribution of the sterols would be observed in the course of the year).
By means of thin-layer chromatography (TLC) of corresponding acetyl derivatives of sterols authors showed, that qualitative composition of sterols from different tissues is identical, but differ quantitatively that indicate on different functional role of sterols in each tissue. We received such data on another mollusks (Mytilus galloprovincialis and Mya arenaria).
According to Piretti investigations (1982), the percentage content of free sterols in different tissues of Scapharca marked difference, making up 78 mg/100g of wet tissue in gills, 73 mg in mantle, around 105 mg in the foot with digestive diverticula and around 120 mg in haemolymph. It appears higher in the cold months.
The high sterols content in the foot together with digestive diverticula may be explained by the fact, that the reproductive organs of the mollusk are present in digestive diverticula. During the collection of mollusk samples of gonads were at a mature age and were rich with lipids. The great cholesterol content in gonads, perhaps, is connected with special physiological state of mollusks, which are productive in steroid hormones in period of sexual activity. As it generally known, cholesterol is a precursor of steroid hormones (Vassalo, 1973; Lubet et al., 1985).
Sterols, were discovered in Scapharca tissues, are the same in qualitative composition as in another bivalve mollusks (Voogt, 1972; Goad, 1978), but differ quantitative.
According to our data, the sterol content in Mytilus galloprovincialis mean quantity higher than in Scapharca that is acclimatizated in Black Sea, but it depends on ecological conditions. So, the total amount of provitamins D3 fluctuates in whole organism of M.galloprovincialis from 2 to 231 mg/100 g wet weight, while in Scapharca - from 9 to 31 mg/100 g wet weight.
Thus, the sterol investigations in different tissues of Scapharca inaequivalvis permit to determine the really quantitative content of it in every separate organ. The qualitative content of sterols is identify in all organs. The quantitative indices of Scapharca sterols indicate that this mollusk is potential source of important biologically active substances of lipid nature, that maybe used for creating of medical preparations, pharmacological substances, also in cosmetic, perfumery and as fodder additions in rations of animals and birds, that raised their weight.
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