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Local substances regulating cochlear blood flow
K Konishi1, H Yamane, H Iguchi
1Department of Otolaryngology, Osaka City University Medical School, Japan.
Abstract:
The regulation of cochlear lateral wall blood flow was investigated in rats using histochemistry, immunohistochemistry and transmission electron microscopy. The contractile protein, tropomyosin (TM) was localized in the pericyte around the vessels of spiral ligament but little was seen around strial capillaries. Prostaglandin I2 (PGI2) is a vasodilatory substance produced by PGI2 synthase (PGI2S), which is present in the endothelium of the vessels of spiral ligament but not much is present around strial capillaries. Endothelial nitric oxide synthase (eNOS) was present in the endothelium of both the vessels of spiral ligament and strial capillaries. These findings indicate that the blood flow of the cochlear lateral wall is regulated mainly in the spiral ligament by locally produced substances and that strial blood flow is not significantly regulated by pericytes responsible for enlargement or constriction of capillaries.
Insights
Cochlear lateral wall blood flow regulation primarily occurs in the spiral ligament via local substances. Strial capillaries are not significantly controlled by pericytes, suggesting distinct regulatory mechanisms.
Area of Science:
- Oto-rhino-laryngology
- Vascular Biology
- Cellular Physiology
Background:
- Cochlear blood flow is crucial for hearing function.
- Mechanisms regulating cochlear lateral wall blood flow are not fully understood.
- Vascular cells and signaling molecules play key roles in microcirculation.
Purpose of the Study:
- To investigate the regulation of cochlear lateral wall blood flow in rats.
- To identify the cellular and molecular players involved in regulating blood flow in the spiral ligament and stria vascularis.
- To differentiate the regulatory mechanisms between spiral ligament vessels and strial capillaries.
Main Methods:
- Histochemistry
- Immunohistochemistry
- Transmission electron microscopy
Main Results:
- Tropomyosin (TM), a contractile protein, was localized in pericytes of spiral ligament vessels but scarce around strial capillaries.
- Prostaglandin I2 synthase (PGI2S), an enzyme producing the vasodilator PGI2, was present in the endothelium of spiral ligament vessels but not significantly around strial capillaries.
- Endothelial nitric oxide synthase (eNOS) was found in the endothelium of both spiral ligament vessels and strial capillaries.
Conclusions:
- Cochlear lateral wall blood flow is mainly regulated in the spiral ligament by locally produced vasoactive substances.
- Strial blood flow regulation appears independent of pericyte-mediated capillary constriction or dilation.
- Distinct microvascular regulatory mechanisms exist between the spiral ligament and stria vascularis in the cochlea.