| Aim Calmodulin-dependent protein kinase II (CaM-PK II), a member of serine-threonine protein kinase family, is an important protein kinase which activated by calmodulin(CaM) and mediates protein phosphorylation in the intracellular signal transduction. It is widely distributed in many tissues and organs and involved in many physiological functions. In this study, we observed the distribution of CaM-PK II in cochlear basilar membrane of normal guinea pig, assessed the CaM-PK II activity level of cochlear basilar membrane and evaluated dynamic changes of CaM-PK II activities in cochlear of presbycusis mice and explosive deafness guinea pigs.Method This study adopt normal guinea pig, C57 and BALB/c inbred mouse strain with presbycusis and explosive deafness guinea pig as animal models, assessed the cochlear hair cells(HC) function by DPOAEs examination, investigated the distribution of CaM-PK II in cochlear basilar membrane by immunohistochemistry technique, detected the CaM-PK II activity by 32P-ATP incorporation method, and observed the structure of HC using scanning electron microscope.Result1. By immunohistochemistry staining, there was CaM-PK II positive reaction in HC of normal guinea pig, with more intensively positive reactions in outer hair cells (OHC) than that in inner hair cells (IHC), which widespread in cytoplasm and negative in nucleus.2. The total activity of CaM-PK II in cochlear basilar membrane of guinea pig is (3.255 ± 0.036) pmol min-1 mg-1, which includes Ca2±/CaM dependent activity (approximate 94.74% of total activity) and Ca2±/CaM independent activity (approximate 5.26% of total activity).3. There were significantly age-related hearing loss in C57 and BALB/c inbred mouse strain. DPOAEs levels trend to decline with age, and there were notable decreases in DPOAEs levels of C57 mice at 60 days old at frequencies of 4.0, 6.0, 8.0 kHz compared with 20 days old (4.0 kHz: -3.17±2.37 vs 3.08 ±1.78 dB SPL, p<0.01; 6.0 kHz: -0.33 ± 2.19 vs 4.75 ± 3.02 dB SPL, p<0.01; 8.0 kHz: -2.08±2.15 vs 3.42±2.02 dB SPL, p<0.01). Furthermore, the descent of DPOAEs levels trend to lower frequencies with age, and there were significant decrease in DPOAEs levels at frequencies ≥2.0 kHz in C57 mice. However, there were significant decreases in DPOAEs levels of BALB/c mice, with earlier coming of hearing loss than C57 mice.4. With scanning electron microscope, we observed that there were well-arranged IHC with brush liked cilia and OHC with bird-wings liked cilia in C57 and BALB/c mice at 20 days old. At 90 days old, there were changes in angle and direction of the OHC cilia in both inbred line, moreover, there was an increased number of OHC that formed the fourth row of OHC in some region of cochlear basilar membrane of both inbred line at 180 days old.5. There were significant decreases in CaM-PKII activity with age. TheCaM-PKH total activities in cochlear basilar membrane of C57 and BALB/c mice at 20 days old were (3.150?.029) pmol 昺in"1 ing"1 and (3.149?.024) pmol ?min-1 ?mg-1, respectively. There were significant decline in C57 and BALB/c mice at 90 days old by 2.32% (PO.05) and 5.97% (PO.05) and at 120 days old by 7.56% (P<0.01) and 15.50% (P<0.01) and at 150 days old by 17.40% (PO.01) and 23.56% (PO.01) and at 180 days old by 20.00% (PO.01) and 34.26 % (P<0.01) compared with 20 days old animals, respectively. The Ca2~VCaM independent activities of CaM-PK II in cochlear basilar membrane of C57 and BALB/c mice at 20 days old were (0.166?.022) pmol min-1 mg-1 and (0.164 ?.026) pmol min-1 mg-1, respectively, and there were significant decrease in the Ca2+/CaM independent activities of C57 and BALB/c mice at 90 days (P<0.05) and 120, 150, 180 days old (P<0.01) compared with 20 days old animals, with constant Ca2+/CaM independent activities and total activities ratio.6. There was significant increase in auditory threshold levels directly after blast in guinea pigs. DPOAEs levels were significantly decreased at frequencies 1 kHz (-12.83 + 2.15 w 2...
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