Cross-talk between apelin and vasopressin in response to different osmotic stimuli in type 2 diabetic rats.

Apelin, a peptide hormone that has been linked to insulin resistance, obesity and glucose metabolism, coexists with arginine vasopressin (AVP) in hypothalamic magnocellular neurons that control body fluid homeostasis. The significant correlation between serum glucose and serum osmolarity in uncontrolled DM indicates the need for adequate compensation, but how apelin and AVP contribute to this is still unsettled. This study aims to investigate the interaction between apelin and AVP in osmotic regulation in type 2 diabetes mellitus (T2DM), and to explore the underlying mechanism. Forty-eight adult male albino rats were divided into six groups: control (isotonic, ip 0.9% NaCl; hypotonic, ip distilled water; hypertonic, ip 2% NaCl) groups and T2DM (isotonic, hypotonic, hypertonic) groups. Serum levels of AVP, apelin, Na, glucose, serum and urine osmolarity were measured; kidney samples were taken for Aquaporin 2 channels (AQP2) and epithelial sodium channel gamma subunit (ENaCγ) gene expression. Hypothalamic tissue sections were used for immunohistochemical staining of apelin and AVP. Both in control and diabetic groups serum apelin, showed a significant negative correlation with serum AVP (r=-0.533, p≤ 0.001). Serum apelin and AVP were inversely proportional to their hypothalamic protein expression. Serum apelin and AVP were significantly higher in diabetic rats (P= 0.001) yet their percentage change in response to hypo and hyper-osmotic stimuli (1.5±0.7, -0.34±0.15 and -0.38±0.13, 1.95±0.36, respectively) was less pronounced when compared to control rats (3.28±0.52, -0.59±0.12 and -0.45±0.13, 2.58±0.93, respectively). Na and ENaCγ levels significantly increased in hypertonic rats, while AQP2 gene expression significantly increased in hypotonic rats. Both apelin and AVP reacted to osmotic stimuli in T2DM but with less sensitivity than in control rats. In spite of its abnormal increased levels in diabetic rats, apelin maintained its role through counteracting AVP action.

Some enzyme interrelationships in serum and organs of Egyptian camel.

In 7 normal healthy Egyptian one-humped camels aged 3-4 years, the relationships were studied between enzyme activities of lactic dehydrogenase (LDH), creatine phosphokinase (CPK), alkaline phosphatase (ALP), acid phosphatase (ACP), and cholonesterase (CHE) of serum and organs as well as between ACP and ALP and between LDH and CPK. Liver, heart, kidney, and spleen tissue samples as well as serum were analysed for total enzyme activity. The following results were obtained: --The heart was the organ with the highest activities of ALP, LDH, and CPK, and it contained high values of CHE, whereas the lowest activities of all enzymes were recorded from serum. The spleen exhibited of the highest activity of ACP. --Each of the serum enzymes ALP, LDH, and CHE were in strong inverse relationship with the corresponding enzymes in the liver. Strong inverse relationships existed also between serum LDH and kidney LDH as well as between CPK in serum and heart. --Direct relationships were remarkable serum LDH and that of spleen and heart as well as between serum ACP and that of liver and heart. --Interrelationships were inverse between ACP and ALP in liver, kidney, and heart, but weak direct interrelationships were characteristic between the 2 enzymes in serum and spleen. --LDH was inversely interrelated with CPK in serum and heart.