Correct option is D
Explanation-
Autoregulation is the process by which blood vessels maintain a relatively constant blood flow despite changes in perfusion pressure. In active tissues, local metabolic changes play a key role.
Statement A- The accumulation of K⁺ locally in active tissues has vasoconstrictor activity - Incorrect.
K⁺ (Potassium ions) released during muscle activity cause vasodilation, not vasoconstriction.
Mechanism: Mild increases in extracellular K⁺ can hyperpolarize vascular smooth muscle, leading to relaxation.
Statement B- The increase in osmolality in active tissues causes vasoconstriction - Incorrect.
Increased osmolality typically causes vasodilation as it signals high metabolic activity. This helps increase blood flow to the area.
Statement C - The accumulation of lactate in active tissues may contribute to vasoconstriction - Incorrect.
Lactate, produced during anaerobic metabolism, is a vasodilator, not a vasoconstrictor.
It helps in increasing blood flow to meet oxygen demands.
Statement D - The hypoxia-inducible factor-1α (HIF-1α) produced due to local fall in O₂ tension in active tissues, initiates the production of different vasodilatory substances - Correct.
HIF-1α is a transcription factor activated under hypoxic conditions. It stimulates production of VEGF, nitric oxide, and other vasodilators to improve oxygen delivery.
Statement E - Histamine released from the damaged cells of active tissues increases capillary permeability - Correct.
Histamine increases capillary permeability and causes vasodilation, facilitating immune cell access and nutrient delivery. It plays a role in inflammation and tissue response.
Correct statement - D and E
So, the correct answer is option d - D and E
