Intrarenal Drug Delivery in Rats: A Method to Deliver Therapeutic Drugs in Rat Kidney via Intra-arterial Injection

Intra-arterial injection facilitates localized delivery to target organs like the kidney while minimizing drug accumulation in other organs. To begin, prep an anesthetized rat in the supine position. Make a small midline incision to expose the peritoneal cavity.

Exteriorize the underlying organs to locate the abdominal aorta. Around the kidney, the aorta branches into the renal artery, between the renal vein and the ureter. Now, remove the connective tissue surrounding the aorta and renal artery.

Clamp the posterior and anterior segments of the aorta to briefly obstruct the blood supply during injection. Gently insert a catheter into the aorta and advance it parallelly into the renal artery. Additionally, connect a syringe filled with the desired drug suspension to the catheter.

Following syringe attachment, inject the suspension into the renal artery. Immediately thereafter, clamp the renal vein and ureter to allow drug distribution within the kidney. A gradual color change in the kidney confirms efficient delivery of the drug suspension.

Next, remove the catheter and apply tissue adhesive to seal the punctured site. Subsequently, remove the clamps from the surrounding vasculature. Return the organs into the body cavity and suture the incision. Allow the rat to recover and regularly monitor for further analysis. 

To begin surgery, ensure that the depth of sedation is adequate by monitoring physical reflexes, such as a withdrawal from a toe pinch. Use a No. 10 surgical scalpel blade to perform a laparotomy through a small midline incision. With cotton swabs, pull the intestine and colon to the right side of the abdomen and cover them with sterile gauze soaked in 0.9% normal saline to keep the organs moist. Gently retract upward the spleen, liver, stomach, and pancreas to expose the aorta and the left kidney artery.

Next, under a surgical microscope, use blunt dissecting curved forceps with a repeated open-close motion along the length of the vessels and sterile cotton swabs to carefully separate the abdominal aorta above and below the left kidney and the left renal artery from the veins, the fat, and the surrounding connective tissue. The use of cotton swabs helps avoid damage to nerves and lymphatic or blood vessels, in particular, to the thin-walled veins.

Then, place a 4-0 silk suture underneath the aorta, and using microvascular clips, clamp the aorta above and below the renal artery bifurcation. Now, using a 24-gauge intravenous catheter, puncture the aorta at the level of the left kidney artery bifurcation and carefully advance the catheter into the renal artery. Because of the small size of the renal artery, the catheter might puncture through the vessel. It is important to work under a surgical microscope and to insert the needle as parallel to the artery as possible.

Then, connect the syringe filled with the drug solution or saline to the catheter and perfuse the kidney. Immediately after perfusion, use a microvascular clip to clamp the left renal vein and the left ureter before removing the catheter. Then, place a piece of absorbable hemostat gelatin sponge with a small drop of tissue adhesive over the punctured area of the aorta, and with a cotton swab, gently apply pressure. At the same time, release the clamp from the aorta below the left renal artery bifurcation.

After 5 minutes, release the clamp from the renal vein and ureter. Carefully release the clamp from the aorta above the left renal artery bifurcation and allow the kidney to reperfuse. The total renal ischemia should last no longer than 7 minutes. After ensuring that no active bleeding occurs and closely observing the area for 10 more minutes, use 4-0 absorbable sutures and a continuous pattern to prevent infection. Enclose the abdominal incision in two layers.

Apply topical antibiotic ointment over the incision area to prevent infections. Then, transfer the rat into the observation cage on a warm pad until complete recovery.