الفهرس 
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Abstract
Whey protein is a mixture of proteins isolated during cheese production and it provides a rapid source of amino acids that can be taken up by the muscles to repair and rebuild muscular tissue. People commonly use whey protein for improving athletic performance and increasing muscle strength, since it plays an important role in protein synthesis and increases lean muscle mass.
The aim of this study was to evaluate the effect of high intake of whey protein with/or without exercise on the histological structure of the liver and skeletal muscle in adult male albino rats.
Twenty adult male albino rats with weight ranged from 150 to 200 grams were used in the current study. They were randomly divided into two groups.
group I (Standard diet group):
Ten rats were received a standard chow diet for the period of the experiment and were further subdivided into two subgroups, five rats each:
• Subgroup IA (Standard diet, sedentary): Rats were left without intervention and were sacrificed after four weeks from the beginning of the experiment.
• Subgroup IB (Standard diet, exercise-trained): Rats were subjected to exercise training during the period of the experiment and were then sacrificed after four weeks.
group II (Whey protein group):
Ten rats were given high dose of whey protein daily (6g/kg) by oral gavage for four weeks and were further subdivided into two subgroups, five rats each:
• Subgroup IIA (whey protein, sedentary): Rats were sacrificed after four weeks.
• Subgroup IIB (whey protein, exercise-trained): Rats were given whey protein within 30 minutes after exercise training for four weeks, then they were sacrificed.
Rats of subgroups IB and IIB were subjected to swimming exercise training in swimming basin for four weeks, five days per week, in which the exercise time was increased gradually throughout the four weeks of the study.
By the end of the experiment (after four weeks), rats from all subgroups were sacrificed under anaesthesia. Liver and gastrocnemius muscles of all subgroups were dissected and subjected to light and electron microscopic studies. Morphometric measurements and statistical analysis for the mean optical density of glycogen granules in PAS sections of liver and gastrocnemius muscle fibers, the mean area percentage of collagen fibers in Masson’s trichrome stained sections of liver and gastrocnemius muscle, and the mean diameter of gastrocnemius muscle fibers in transverse sections stained by H&E.
High dose whey protein administration, in subgroup IIA (whey protein, sedentary), resulted in profound degenerative histological and morphometrical changes of liver tissue as compared to subgroup IA (standard diet, sedentary). Mononuclear cellular infiltration and congestion in central vein were observed. Most of the hepatocytes showed vacuolated cytoplasm, decreased basophilic bodies, and eccentric pyknotic nuclei or even karyorrhectic nuclei. This was confirmed by electron microscopic examination which revealed the presence of vacuolated cytoplasm containing irregular, shrunken, and heterochromatic electron dense nucleus with distorted mitochondria. The mean area percentage of collagen fibers in liver sections was significantly increased as compared to those of subgroups IA (standard diet, sedentary), IB (standard diet, exercise- trained), and IIB (whey protein, exercise- trained). Moreover, the mean optical density of liver glycogen granules was significantly increased as compared to those of subgroup IA (standard diet, sedentary), and IB (standard diet, exercise- trained). Most of the muscle fibers of rats’ gastrocnemius muscle of subgroup IIA showed acidophilic sarcoplasm with peripheral flattened nuclei and few centrally located nuclei were seen in few muscle fibers; however, the mean gastrocnemius muscle diameter showed non-significant increase when compared to subgroup IA (standard diet, sedentary).
Regarding liver sections of both exercise-trained subgroups, light microscopic examination of the liver sections revealed that subgroup IB (standard diet, exercise-trained) showed hepatic architecture nearly similar to that of subgroup IA (standard diet, sedentary). No hepatic tissue injury was observed. This was confirmed by electron microscopic examination which showed that the ultra-structure of the hepatocytes was comparable to that of subgroup IA (standard diet, sedentary). There was non-significant decrease in mean optical density of hepatocytes’ glycogen granules by morphometric and statistical analysis as compared to subgroup IA (standard diet, sedentary). In subgroup IIB (whey protein, exercise-trained), the administration of whey protein in association with exercise training led to marked amelioration of the degenerative effects of high intake of whey protein on the liver. Minimal cellular infiltration around portal areas were observed. The hepatocytes showed minimal cytoplasmic vacuolations and vesicular nuclei. These findings were confirmed by the electron microscope examination which showed hepatocytes with euchromatic nuclei. Also, mitochondria appeared nearly similar to that of subgroup IA (standard diet, sedentary) and IB (standard diet, exercise-trained). The mean optical density of liver glycogen granules in subgroup IIB showed significant increase as compared to all other studied subgroups.
As regards the gastrocnemius muscle in both exercise-trained subgroups, central nuclei and splitting were observed in some muscle fibers, which was more pronounced in subgroup IIB (whey protein, exercise-trained) than in subgroup IB (standard diet, exercise-trained). In addition, subgroup IIB showed significant increase in the mean diameter of muscle fibers and in the mean optical density of muscle glycogen granules when compared to all other studied subgroups. There was a non-significant decrease in the mean area percentage of collagen in gastrocnemius muscle fibers in swimming exercise-trained subgroups (IB and IIB) when compared to sedentary subgroups (IA and IIA)
Consequently, it was concluded that high intake of whey protein without physical exercise has its degenerative effects on liver, also it showed non-significant increase in mean diameter of skeletal muscle as compared to rats fed standard diet. Thus, whey protein should be taken within its recommended dose and accompanied by physical exercise.